Emerging Technologies

Hydrogen Fuel Cells

For more than 150 years, scientists have known that when hydrogen and oxygen combine to form water (H2O), the chemical reaction releases electrical energy. (It’s exactly the reverse of electrolysis, in which running a current through water separates H2O into its constituent elements.) Devices that use a controlled combination of the two gases to generate current are called fuel cells. This developing technology underlies the vision of a nationwide “hydrogen economy,” in which the only exhaust from fuel-cell-powered vehicles would be water vapor, and America would drastically reduce its dependence on foreign fuel supplies.

This developing technology underlies the vision of a nationwide “hydrogen economy,” in which the only exhaust from fuel-cell-powered vehicles would be water vapor, and America would drastically reduce its dependence on foreign fuel supplies.

There are several significant obstacles to achieving that vision. Present fuel cells are too expensive and unreliable for the mass market. And hydrogen is very difficult to store and transport in a vehicle unless it is compressed to thousands of pounds per square inch (psi). Automotive companies are using containers in their demo vehicles that can store hydrogen at 5,000 to 10,000 psi, but a cost-effective and safe distribution system would have to be put in place before these vehicles could become widely available.

Furthermore, hydrogen (like electricity) is not a primary source of energy but rather an energy carrier. There are no natural reservoirs of pure hydrogen; it must be extracted from compounds such asnatural gas or water. And the processes for separating it from these principal sources pose their own challenges. When natural gas (basically methane, a lightweight molecule made of carbon and hydrogen) is exposed to steam under high temperatures in the presence of a catalyst, it frees the hydrogen. However, the process itself also produces substantial amounts of CO2. Widespread use would require a carbon sequestration scheme.

Significant public and private research on fuel cells has been conducted to accelerate their development and successful introduction into the marketplace. And hydrogen-fuel-cell cars are receiving considerable attention in the press. Some car manufacturers, including General Motors and Honda, are putting a very limited number of these vehicles on the road. There are hydrogen fueling stations in about 16 states, the greatest number being in California. Most of these, though, are small, private facilities intended to support a few experimental vehicles.

Not all hydrogen fuel cells are destined for vehicles. Stationary fuel cells for electric power generation have also been under development for decades. Some applications of fuel cells to residential or commercial buildings could involve generating electricity from a fuel input like natural gas or hydrogen and using the waste heat from that process to heat the building. Such co-generation systems could be very efficient in meeting both the electrical and heating needs of buildings. Still, costs remain high and there are numerous technical challenges to overcome with these systems. It will take decades of research and development, as well as changes in the energy infrastructure, before a hydrogen economy on a broad scale can be achieved.

How We Use Energy

Transportation

In the United States we use 28% of our energy to move people and goods from one place to another. The transportation sector includes all modes of transportation—from personal vehicles (cars, light trucks) to public transportation (buses, trains) to airplanes, freight trains, barges, and pipelines. One might think that airplanes, trains, and buses would consume most of the energy used in this sector but, in fact, their percentages are relatively small—about 9% for aircraft and about 3% for trains and buses. Personal vehicles, on the other hand, consume more than 60% of the energy used for transportation.

Over the past century, dependence on vehicles burning petroleum-based fuels has become a defining component of American life, bringing countless benefits. In fact, the United States, with less than 5% of the world’s population, is home to one-third of the world’s automobiles. In 2007, automobiles, motorcycles, trucks, and buses drove nearly 3 trillion miles in our country—about the equivalent of driving to the sun and back 13,440 times. Over the next 20 years, the total number of miles driven by Americans is projected to grow by 40%, increasing the demand for fuel.

Over the next 20 years, the total number of miles driven by Americans is projected to grow by 40%, increasing the demand for fuel.

86% of all the energy used in this sector comes from gasoline and diesel fuels, a troubling fact. Combustion of gasoline and diesel fuel emits carbon dioxide, as well as particulate matter, oxides of nitrogen (a prime component of “smog”), carbon monoxide, and unburned hydrocarbons. Indeed, whenever any fossil fuels are burned, carbon dioxide is released into the atmosphere, where it functions as a heat-trapping greenhouse gas. Also of concern is that we are dependent on foreign sources for two-thirds of our oil supplies.

Efforts are already well under way to find suitable alternatives to oil.Biofuels are one possibility. Alternative types of vehicles—hybrids,electric vehicles, and vehicles powered by hydrogen fuel cells, for example—all have the goal of reducing our dependence on oil. Petroleum sources that could serve as alternatives to conventional oil, such as oil shale and tar sands, could reduce our dependence on foreign oil, but wouldn’t help solve the environmental issues surrounding burning fossil fuels. Mining these resources can have damaging environmental effects, as well. Converting coal to liquid fuel is another option but it, too, has significant implications on the environment. The AEF committee estimates that the coal-to-liquid plants could replace up to 3 million barrels of gasoline per day by 2035 but that would require a 50% increase in U.S. coal production.

Greater vehicle efficiency may be our greatest short term strategy for reducing demand for petroleum. The CAFE standards, initially adopted in 1975, made more stringent in 2007, and strengthened again in pending legislation, require automobile manufacturers to build cars with higher average fuel economy.

Explore Our Energy System to see how the transportation sector fits in with the rest of the energy flow in the United States.

Power from Two Energy Sources?

Alternative sources of energy are clean and green but the catch is they generate less energy compared to fossil fuels. So now the scientists are trying to use different sources of alternative energy at the same place and same time to generate power. Attempts are being made to combine two forms of external energy sources such as light and heat or light and vibration to generate external energy so that enough energy can be collected for practical use. Fujitsu Laboratories have now succeeded in using hybrid energy sources to generate power. Fujitsu Laboratories wants to provide this technology for commercial use by the year 2015

Fujitsu Laboratories: Making power from two sources of energy
Fujitsu Laboratories are working extensively in this regard, and to generate electricity both from heat and light, they are creating a new hybrid energy harvesting device. Energy harvesting is the procedure used in accumulating energy from the environment. Later on that energy is transformed into electricity. Fujitsu is not doing something innovative. Work in this field was done by scientists earlier too. But hybrid energy could only be generated by combining separate devices and that proved costly so it was commercially unviable.

Reducing the cost
Now Fujitsu laboratories confirm that two separate devices are not needed to generate electricity from a hybrid source. How were they successful in reducing costs? They used organic materials for creating hybrid device. This lowers the cost, and the new technology is showing promise to convert energy from the environment to electricity. The device from Fujitsu Laboratories is just a one-piece device that catches energy from the most common form of energy available for large scale use.

The use of organic material
An organic material of high efficiency that can generate power from both photovoltaic and thermoelectric mode has been developed by Fujitsu Laboratories. This organic material can make power both from heat in thermoelectric mode and indoor lighting in photovoltaic mode. The production cost is very low because of the organic materials and the processing costs are very low. The device can be made to work as a thermoelectric generator or photovoltaic cell by changing the electrical circuit connecting P-type and N-type semiconductors.

Advantages of the technology

• It helps to get energy from two different sources by using one device.
• The technology enables the use of alternative energy and sensors in the areas, where till now it was forbidden. It can now power medical sensing technology and sensor networks. It can sensor those monitors without any battery or electric wire that are used to check conditions like, heartbeats, body temperature and blood pressure.
• There is no need for battery or electric wire.
• Because this technology is not costly, it can be widely used.
• This technology is a very efficient way of gathering energy from external sources.
• Since the device works with the help of both heat and light, it will continue to work if one of these energy sources remains unavailable.
• It can work in remote areas.
• It can help to forecast environmental conditions.

For Fujitsu Laboratories, combining two different sources of generating energy to produce power is just the beginning. They want to make this technology more efficient so that by combining two sources of producing energy, hybrid equipment can be made to work better.

Local Solar Rules Can Save You Big Bucks

The price of an average U.S. home solar power system is about $20,000. (That’s before a 30 percent federal tax credit and any state, local and/or utility incentives.) If the price were to drop to $17,000, or even $16,000, would you be buying?

A new report out last week from Lawrence Berkeley National Laboratory (LBL), called “How Much Do Local Regulations Matter?” demonstrates that such steep declines are possible in the near term, even without any technological advances. (The same day, LBL released two other studies on solar, one of which I blogged on here.)  In fact, good local solar policies that cover everything from permitting — that is, getting local building department sign-off to install a solar system — to inspections and interconnection (getting your system connected to the electric grid) — can make a difference in home solar costs of as much as 15 percent. In other words, they can save the average homeowner installing a five kilowatt system an average of $2,500 or more.

The LBL researchers and their colleagues at Yale, the University of Texas at Austin, and the U.S. Department of Energy have concluded all this by analyzing two sets of data. One, about local permitting procedures and costs, was collected by our friends at Vote Solar, through their Project Permit program. (More on that later.) The other comes from the DOE’s Rooftop Solar Challenge, which brings “together local officials, utilities, private industry, nonprofits, and other stakeholders to simplify the solar installation process.” Like Vote Solar, the RSC collects data on permitting costs. But it also examines interconnection fees and processes, the availability to net metering, which allows solar owners to sell excess power back to the grid at a fair price, and financing options, planning and zoning issues.

After grinding through the data, the researchers found that cities, towns and other authorities with pro-solar permitting procedures alone can save homeowners between $700 and $900 per home system. That makes sense: If installers can file their permit applications online, and get approval that way, too, that saves them money that they can pass along to consumers. (Compare it to sending an employee down to the local buildings department to wait in line and you understand the cost savings.) The same goes for the number of new system inspections required and the time window installers have to leave open for inspectors to visit.

When you factor in questions like whether homeowners can sell excess power back to the grid, and whether their state or county allows third-party developers to install and own systems on homes and then sell the electricity back to the homeowner at a discount, through a process called a power purchase agreement, or whether similar solar leases are allowed, the savings differences can grow significantly.

What does all that mean for us solar activists and/or would-be solar homeowners? It means there’s a lot we can do at the local and state level to keep solar prices falling into the very affordable range. (Think about it: A $16,000 home solar system, which lasts at least 25 years? That’s cheaper than many used cars.)  At the local level, we can work with our mayors, our city councils and our local buildings departments to help streamline solar permitting procedures. (Vote Solar’s Project Permit can help. It collects information about local solar permitting rules and offers advice and best practices for changing them.) New York, for instance, offers a unified solar permit that any Empire State village, town or city can adopt. Enough nudging from residents can make that happen.

At the state level, there’s much to be done, whether it’s promoting legislation that will allow power purchase agreements and solar leasing in the states where they’re not currently allowed. Or, protecting or expanding net metering, which is a hot topic these days in many state legislatures and public utility commissions. Bringing all this to fruition is likely far easier than passing legislation in our gridlocked Congress.

So, got some energy? Get involved. Remember: The cheaper solar gets, the faster it’s deployed. And the faster it’s deployed, the better able we are to fight climate change, create good, local jobs in the rapidly growing solar industry, and clean the air our kids breathe.

“How much do local solar regulations matter?” LBL’s new report asks. The answer is: a whole heck of a lot.

California’s Conservation Proposal Kneecaps Utility-scale Solar

Six years in the making, state and federal agencies released five options with a “Preferred Alternative” draft for the Desert Renewable Energy and Conservation Plan (DRECP), potentially kneecapping development in the best solar region in the U.S. by cutting off previous access to public lands and reducing eligible acreage by two thirds.

The amount of clean energy allowed on 22 million acres of California desert will be finalized in 2016 after addressing public comments at 10 public meetings until November 13th. The final version then becomes law for a quarter century.

The detailed options were hammered out between two state and two federal agencies, the U.S. Fish and Wildlife Services (USFWS), the California Department of Fish and Wildlife (CDFW), the California Energy Commission (CEC), and the federal Bureau of Land Management (BLM).

The idea was to resolve conflicts over accommodating enough clean energy to meet California’s climate goals as well as to create new conservation and recreation areas on California desert land. The goal was to reduce both interagency and local obstacles that have impeded desert clean energy projects by siting near transmission, on disturbed private land, while also preserving sensitive habitat. 

Under the drafters’ Preferred Alternative only 20 percent of acreage would be on public lands, reversing the Obama Administration's original plan to expand renewable energy on BLM land

Fatal Weakness: "The Invisible Hand" 

The preferred proposal would allow renewables on 2 million acres in patches throughout the 22 million-acre region, in theory leaving space for up to 20 GW of renewables to be developed if needed by 2040. However, 80 percent must be on privately owned land. There is no guarantee that every land owner would rent or keep rates reasonable, so meeting climate goals relies on "the invisible hand" of the market. 

Under the No Action Alternative option, there had been 6 million acres available — most on public land.DRECP Alternative 2, the “Geographically Balanced/Transmission Aligned Alternative”  would allow slightly more development on public land at 33 percent, and a total 2.5 million acres. But Alternative 1 would allow only 14 percent on public land, and limit renewables to 1 million acres. (The acreage is dotted in clumps throughout the bottom quarter of the state.) 

Pink indicates former BLM land available under the DRECP No Action Alternative.

CALWEA states that most potential acreage under the Preferred Alternative doesn’t turn out to be actually available. (Neither the wind industry nor solar industry DRECP options made it to the final alternatives.) And DRECP also rolls back previous flexibility over variance lands. 

“Even within the 2 million acres, the DRECP avoidance and mitigation standards that projects would be subjected to — such as quarter mile ephemeral stream setbacks — would make solar development almost impossible,” said utility-scale PV permitting attorney Andrew Bell of Marten Law.

“Unlike under previous BLM rules, there is no mechanism for using site-specific data to correct the landscape-scale mapping assumptions of the plan, which necessarily will be under-inclusive in some areas and over-inclusive in others,” added Bell. 

Particularly hard hit by the new limits is Concentrated Solar Power (CSP), which uses the sun to run steam-driven turbines. CSP is only suited to utility-scale siting in desert regions, and California’s deserts have some of the best potential on earth.

Governor Brown also cautioned: “Once the plan is in place, it will be difficult to add more development if the amount of renewable energy needed to stave off the worst impacts of climate change is underestimated.”

Most Difficult Permitting in the World

Attempting to mine the sun or wind in California is not for the faint of heart. Clean energy permitting in California was already felling more projects than those that made it through. Filings with one of these agencies alone can amount to up to 500-page legal documents taking five years or more to process. By contrast, those that want to drill California’s BLM lands for oil or gas just fill out a two page form.

In 2010 the BLM gave nine permits for renewables and 1,308 for oil and gas. 

Only oil and gas on public land is seen as a "resource," yet California must meet climate goals. Permitting rules were already stacked against clean energy due to these conflicting charters by the agencies. BrightSource Energy singled out the CEC for praise.

“I give credit to the agencies for trying to bring some balance in this process, I really do,” said BrightSource Energy SVP of government affairs Joe Desmond, a former CEC Chair himself. 

Faulty Information Influencing Decision

The DRECP public meetings follow widely disseminated and faulty information establishing the truthiness that CSP is “frying 28,000 birds” at America’s first commercial-scale power tower CSP plant in America. 

“There's no question that the issue has been, in some corners, perhaps exaggerated or mischaracterized,” said Desmond. “Birds don't vaporize. The data showed us that the area of concern associated with solar flux only occurs near the tower, which helps us focus avian deterrent efforts for maximum effect.”

(The actual numbers of singed birds were actually in the hundreds, and are now reduced with bird deterrents.)

“But people will be going to these meetings in California thinking it's 28,000,” said Tex Wilkins, who, as a veteran of the Department of Energy solar program experienced public opposition that wound up greatly limiting the BLM and DOE solar PEIS regions. 

“There needs to be somebody there that can say wait a minute; the actual number will be close to several hundred. Having correct information at these meetings would tend to maybe decrease some of the complaints about the technologies based on faulty information,” said Wilkins.

“It’s important to keep these issues in perspective. The primary risks to birds certainly aren’t solar projects,” said SolarReserve CEO Kevin Smith. “This year in Southern California almost every raptor nest failed because of drought. An Audubon study found that more than half of the bird population in North America is at risk of extinction due to climate change.”

Other states, with less difficult permitting, already host the first two CSP projects to include storage and replace fossil energy. In Arizona, Abengoa’s Solana CSP project now ships power on demand at night and before sunrise, reducing coal use by APS. In Nevada, SolarReserve’s Crescent Dunes CSP project is contracted to supply Las Vegas till midnight with 500,000 megawatt-hours annually — providing solar after dark.

Researchers Developing Supercomputer to Tackle Grid Challenges

"Big data" is playing an increasingly big role in the renewable energy industry and the transformation of the nation's electrical grid, and no single entity provides a better tool for such data than the Energy Department's Energy Systems Integration Facility (ESIF) located on the campus of the National Renewable Energy Laboratory (NREL). Imagined by NREL leaders who foresaw the possibilities for high performance computing (HPC), the ESIF's HPC data center is fulfilling the goal of handling large and complex datasets that exceed traditional database processes.

"Big data" is playing an increasing role in the renewable energy industry and the transformation of the nation's electrical grid. NREL's Peregrine supercomputer is already fulfilling the goal of handling large and complex datasets that exceed traditional database processes. Photo by Dennis Schroeder, NREL

"As industry moves forward to integrate all these renewables, big data is a key piece of the puzzle," ESIF Business Development Manager Martha Symko-Davies said. "The links between modeling and simulation, hardware, and good, bad, and aggregated data—all parts of the whole puzzle — are captured at the ESIF through big data." That's why the ESIF's Peregrine supercomputer, dedicated by Energy Secretary Ernest Moniz in September 2013, is so important; it can do more than a quadrillion calculations per second as part of the world's most energy-efficient HPC data center.

Asking the Big Questions

Located adjacent to NREL's high performance computing data center, the ESIF Insight Center uses advanced visualization technology to provide on-site and remote viewing of experimental data, high-resolution visual imagery, and large-scale simulation data. Photo by Dennis Schroeder, NREL

"Peregrine provides much-needed computational capability to model complex systems such as the grid, to allow us to ask 'what if' questions, and to optimize how these systems are designed and deployed with much higher confidence in their efficiency and robustness," NREL Computational Science Center Director Steve Hammond said.

Increasingly, those "what ifs" involve the challenge of delivering distributed energy to the grid when the sun shines and the wind blows, while making it  even more reliable than when the grid was a one-way delivery system of fossil-fuel-based energy. "By focusing on the integration and optimization of energy systems across the energy infrastructure, we can better understand and make use of potential co-benefits that increase reliability and performance, reduce cost, and minimize environmental impacts," NREL Director of Energy Systems Integration (ESI) Ben Kroposki said.

This focus will help map the pathway NREL will pioneer with the Energy Department to modernize the nation's electrical grid. The ESIF "will be a major focus of DOE to help us transform the energy system to the one we need in 2030," Moniz told the audience at the ESIF's dedication. The ESIF is "the step up we need to elevate energy systems integration," he said.

Thanks to the capacities of the ESIF and Peregrine, efforts are underway at NREL to move commercial-scale research and development and testing forward. In January 2014, NREL began to assemble a virtual link from the ESIF to NREL's National Wind Technology Center and other national labs and universities. "We're setting up this virtual network so that we can tap into other's resources and knowledge and not try to recreate it here at NREL," NREL Associate Laboratory Director for ESI Bryan Hannegan said.

NREL isn't working alone, Symko-Davies noted. "Researchers here, coupled with Energy Department efforts, and external partners — large and small companies, utilities, academia, policymakers, and others — are all helping to collectively solve problems."

ESIF and NREL's Partners Work Together

Energy Secretary Ernest Moniz, right, joins NREL Director Dan Arvizu, center, and NREL Computational Science Center Director Steve Hammond, left, at the unveiling of Peregrine. NREL collaborated with HP and Intel to develop an innovative warm-water, liquid-cooled supercomputer. Peregrine resides in the new ESIF data center and will help tackle the challenges of energy systems integration. Photo by Dennis Schroeder, NREL

Collaboration is key, and it is hard-wired into the ESIF's core. NREL teamed with Hewlett-Packard (HP) and Intel to develop the innovative warm-water, liquid-cooled Peregrine supercomputer.

The HP Apollo liquid-cooled supercomputing platform provides the foundation for numerical modeling and simulations, which allow scientists to gain new insights into a wide range of topics. However, as HPC systems scale up by orders of magnitude, energy consumption and heat dissipation stress the supporting systems and the facilities in which they are housed. With NREL's HPC data center, 90 percent or more of the computer's waste heat is captured and reused as the primary heat source for ESIF offices and laboratory space.

The ESIF truly was designed for partners — and NREL and its world-class facilities have made it known that they are open for business. "We've known that industry was eager for a place like the ESIF, which allows utility companies and investors to see technology working in real time and on a large scale," NREL Director Dan Arvizu said.

For example, Advanced Energy Industries is accessing the ESIF's Power Systems Integration Laboratory to test its new solar photovoltaic (PV) inverter technology with the facility's hardware-in-the-loop system and megawatt-scale grid simulators. The company's inverter will help support a smarter grid that can handle two-way flows of power and communication while reducing hardware costs.

Given the nature of global climate change, it's vital that the ESIF has a long reach. In a recent joint initiative between the U.S. Navy and the lab, NREL successfully demonstrated a new custom-engineered energy management system to maximize solar PV on a naval base in Hawaii while smoothing the effects of variable solar PV generation by charging and discharging batteries.

As demand for the ESIF expands, it helps another key area of growth: commercialization. "When industry and NREL work closely together, great things happen. The abilities of the ESIF allow manufacturers, industry, and the clean energy sector to bring new ideas to market," NREL Associate Laboratory Director for Innovation, Partnering, and Outreach Bill Farris said.

And it appears likely that the ESIF and its HPC capabilities will be in increasing demand in coming years. The word is already out on the one-year-old lab facility, which is home to 200 scientists and engineers — and the editors of R&D Magazine have named it the 2014 Laboratory of the Year.

Not surprisingly, the ultra-efficient HPC data center gets the spotlight. It helped NREL earn a 2013 U.S. Department of Energy Sustainability Award for its leadership in green information technology, including the lab's electronic stewardship practices and world-class HPC data centers.

The ESIF and Peregrine model what the future holds for the grid and energy systems, while helping industry and partners find a path to commercializing the technology needed to make that transformation.

That's enough to make an energy secretary smile.

Steam from the Sun

Cambridge, Mass. -- A new material structure developed at MIT generates steam by soaking up the sun. The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.

The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation. What’s more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.

Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials — a particular advantage for a variety of compact, steam-powered applications.

On the left, a representative structure for localization of heat; the cross section of structure and temperature distribution. On the right, a picture of enhanced steam generation by the DLS structure under solar illumination. Courtesy of the researchers.

“Steam is important for desalination, hygiene systems, and sterilization,” says Ghasemi, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”

Ghasemi and mechanical engineering department head Gang Chen, along with five others at MIT, report on the details of the new steam-generating structure in the journal Nature Communications. 

Cutting the Optical Concentration

Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.

Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy — about 1,000 times that of an average sunny day.

By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day — the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.  

“This is a huge advantage in cost-reduction,” Ghasemi says. “That’s exciting for us because we’ve come up with a new approach to solar steam generation.”

From Sun to Steam

The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid’s surface.

After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is “just like popcorn”: The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.

The structure’s bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.

As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.

The DLS that consists of a carbon foam (10-mm thick) supporting an exfoliated graphite layer (B5-mm thick). Both layers are hydrophilic to promote the capillary rise of water to the surface. Courtesy of the researchers.

The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator — a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.

Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.

“There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations,” Ghasemi says. “There is still a lot of research that can be done on implementing this in larger systems.”

Simulation Models Optimize Hydropower Potential

Researchers at the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB in Ilmenau are developing information technology to make water power generation systems more efficient. The Advanced System Technology (AST) department is creating simulation and optimization models that consolidate external factors such as weather data, water levels and market prices with system infrastructure and generate optimized plans for operational facilities, such as the opening and closing of sluice gates, reservoir water level regulation and hydro turbine operation.

This information helps the operator to fine-tune each hydroelectric power station’s generating power to meet current energy economics and to sell the generated power for the highest possible return.  

The hydroelectric plants in the Columbia River basin in the Pacific Northwest generate 22,000 MW in output. In the photo: a dam wall in the many-branched dam system. Credit: Fraunhofer IOSB

22,000 MW in the Columbia River Basin

Following projects in Germany and China, and in cooperation with the Dutch-American company Deltares, IOSB researchers are now applying their expertise to one of the world’s largest hydropower operators. The Bonneville Power Administration (BPA) in the northwest of the United States runs a complex and extensive dam system in the Columbia River basin that collectively generates around 22,000 megawatts (MW). This is more than five times the output in Germany, which operates some 7500 hydroelectric plants on rivers and lakes and generates 4300 MW.

More than 12 million people live in the BPA’s catchment area, which covers parts of the U.S. states Oregon, Washington, Montana, California, Nevada, Utah and Wyoming. Together with Deltares, researchers on the HyPROM project have developed a functioning simulation and optimization model that ensures the best possible operation of the BPA dam system based on predefined parameters.

Very different parameters come into play when it comes to generating hydroelectric power — rainfall levels, volume and speed of the water, not to mention general climate factors. At the same time, regulations regarding the protection of fish, flood control or environmental guidelines have to be accommodated.

Hydroelectric plants can be operated optimally only when you take all the variables into account. As an additional challenge, HyPROM takes on the complexity of the extensively networked Columbia River basin dam system — it covers two different rivers with an average water flow of 7,500 cubic meters per second, ten hydro plants, ten reservoirs and an altitude difference of 350 meters.

Currently, researchers are working on expanding the simulation and optimization model to better encompass energy-economic aspects, bearing in mind the fluctuating availability of wind and solar energy as well as randomly changing market prices. Then we can incorporate even more information in our calculations. This creates a scenario that comes much closer to reality.

The project partners plan to integrate the newly developed technology into a system that will help employees to make the right decisions in running the facility. The aim for the future is to enable BPA to adjust its entire control and management system in under an hour to react to changing circumstances. That way, BPA could choose to sell hydroelectric power only when the price is right. At other times, it could replenish its reservoirs to empty them later, when it makes economic sense or is technically necessary.

For operators who sell not only hydroelectric energy but also other energy sources with a fluctuating supply, such as wind and solar energy, the price is an especially important factor.

Recycling Old Batteries into Solar Cells

Cambridge, Mass. -- This could be a classic win-win solution: A system proposed by researchers at MIT recycles materials from discarded car batteries — a potential source of lead pollution — into new, long-lasting solar panels that provide emissions-free power.

The system is described in a paper in the journal Energy and Environmental Science, co-authored by professors Angela M. Belcher and Paula T. Hammond, graduate student Po-Yen Chen, and three others. It is based on a recent development in solar cells that makes use of a compound called perovskite — specifically, organolead halide perovskite — a technology that has rapidly progressed from initial experiments to a point where its efficiency is nearly competitive with that of other types of solar cells.

“It went from initial demonstrations to good efficiency in less than two years,” says Belcher, the W.M. Keck Professor of Energy at MIT. Already, perovskite-based photovoltaic cells have achieved power-conversion efficiency of more than 19 percent, which is close to that of many commercial silicon-based solar cells.

Initial descriptions of the perovskite technology identified its use of lead, whose production from raw ores can produce toxic residues, as a drawback. But by using recycled lead from old car batteries, the manufacturing process can instead be used to divert toxic material from landfills and reuse it in photovoltaic panels that could go on producing power for decades.

Amazingly, because the perovskite photovoltaic material takes the form of a thin film just half a micrometer thick, the team’s analysis shows that the lead from a single car battery could produce enough solar panels to provide power for 30 households.

As an added advantage, the production of perovskite solar cells is a relatively simple and benign process. “It has the advantage of being a low-temperature process, and the number of steps is reduced” compared with the manufacture of conventional solar cells, Belcher says.

Those factors will help to make it “easy to get to large scale cheaply,” Chen adds.

Battery Pileup Ahead

One motivation for using the lead in old car batteries is that battery technology is undergoing rapid change, with new, more efficient types, such as lithium-ion batteries, swiftly taking over the market. “Once the battery technology evolves, over 200 million lead-acid batteries will potentially be retired in the United States, and that could cause a lot of environmental issues,” Belcher says.

Today, she says, 90 percent of the lead recovered from the recycling of old batteries is used to produce new batteries, but over time the market for new lead-acid batteries is likely to decline, potentially leaving a large stockpile of lead with no obvious application.

In a finished solar panel, the lead-containing layer would be fully encapsulated by other materials, as many solar panels are today, limiting the risk of lead contamination of the environment. When the panels are eventually retired, the lead can simply be recycled into new solar panels.

“The process to encapsulate them will be the same as for polymer cells today,” Chen says. “That technology can be easily translated.”

as New

Belcher believes that the recycled perovskite solar cells will be embraced by other photovoltaics researchers, who can now fine-tune the technology for maximum efficiency. The team’s work clearly demonstrates that lead recovered from old batteries is just as good for the production of perovskite solar cells as freshly produced metal.

Some companies are already gearing up for commercial production of perovskite photovoltaic panels, which could otherwise require new sources of lead. Since this could expose miners and smelters to toxic fumes, the introduction of recycling instead could provide immediate benefits, the team says.

The work, which also included research scientist Jifa Qi, graduate student Matthew Klug and postdoc Xiangnan Dang, was supported by Italian energy company Eni through the MIT Energy Initiative.

Turning Humble Seaweed to Biofuel

The sea has long been a source of Norway’s riches, whether from cod, farmed salmon or oil. Now one researcher hopes to add seaweed to this list as he refines a way to produce “biocrude” from common kelp.

Kelp can be turned into a kind of "bio-crude" that can be further refined into a biofuel. Credit: Rune Petter Ness, NTNU Communication Division

“What we are trying to do is to mimic natural processes to produce oil,” said Khanh-Quang Tran, an associate professor in Norwegian University of Science and Technology's (NTNU) Department of Energy and Process Engineering. “However, while petroleum oil is produced naturally on a geologic time scale, we can do it in minutes.”

Tran conducted preliminary studies using sugar kelp (Laminaria saccharina), which grows naturally along the Norwegian coast. His results have just been published in the academic journal Algal Research.

Learn about more kelp biofuel initiatives here.

The Breakthrough

Using small quartz tube “reactors” — which look like tiny sealed straws — Tran heated the reactor containing a slurry made from the kelp biomass and water to 350 degrees C at a very high rate of 585 degrees C per minute.

The technique, called fast hydrothermal liquefaction, gave him a bio-oil yield of 79 percent. That means that 79 percent of the kelp biomass in the reactors was converted to bio-oil. A similar study in the U.K. using the same species of kelp yielded just 19 percent. The secret, Tran said, is the rapid heating.

Falling Short on Biofuel Production

Biofuel has long been seen as a promising way to help shift humankind towards a more sustainable and climate friendly lifestyle. The logic is simple: petroleum-like fuels made from crops or substances take up CO2 as they grow and release that same CO2 when they are burned, so they are essentially carbon-neutral.

In its report “Tracking Clean Energy Progress 2014,” the International Energy Agency (IEA) says that biofuel production worldwide was 113 billion litres in 2013, and could reach 140 billion litres by 2018.

That may sound like a lot — but the IEA says biofuel production will need to grow 22-fold by 2025 to produce the amount of biofuel the world will need to keep global temperatures from rising more than 2oC.

The problem is the biomass feedstock. It’s relatively easy to turn corn or sugar beets into ethanol that we can pump right into our petrol tanks. But using food biomass for fuel is more and more problematic as the world’s population climbs towards 8 billion and beyond.

To get around this problem, biofuel is now produced from non-food biomass including agricultural residues, land-based energy crops such as fast-growing trees and grasses, and aquatic crops such as seaweed and microalgae.

All of these feedstocks have their challenges, especially those that are land based. At least part of the issue is the fact that crops for biofuel could potentially displace crops for food.

However, seaweed offers all of the advantages of a biofuel feedstock with the additional benefit of growing, not surprisingly, in the sea.

Scaling Up

But turning big pieces of slippery, salty kelp into biocrude is a challenge, too. Some studies have used catalysts, which are added chemicals that can help make the process go more quickly or easily. However, catalysts are normally expensive and require catalyst recovery.

The UK study that resulted in a 19 percent yield used a catalyst in its process.

Tran says the advantage of his process is that it is relatively simple and does not need a catalyst. The high heating rate also results in a biocrude that has molecular properties that will make it easier to refine.

But Tran’s experiments were what are called screening tests. He worked with batch reactors that were small and not suitable for an industrial scale. “When you want to scale up the process you have to work with a flow reactor,” or a reactor with a continuous flow of reactants and products, he said. “I already have a very good idea for such a reactor.”

The Outlook

Even though the preliminary tests gave a yield of 79 percent, Tran believes he can improve the results even more. He’s now looking for industrial partners and additional funding to continue his research.

All-in-One Solution: Solar that Stores Its Own Power

Columbus, Ohio — Is it a solar cell? Or a rechargeable battery? Actually, the patent-pending device invented at The Ohio State University is both: the world’s first solar battery.

In the October 3, 2014 issue of the journal Nature Communications, the researchers report that they’ve succeeded in combining a battery and a solar cell into one hybrid device.

Key to the innovation is a mesh solar panel, which allows air to enter the battery, and a special process for transferring electrons between the solar panel and the battery electrode. Inside the device, light and oxygen enable different parts of the chemical reactions that charge the battery.

The university will license the solar battery to industry, where Yiying Wu, professor of chemistry and biochemistry at Ohio State, says it will help tame the costs of renewable energy.

“The state of the art is to use a solar panel to capture the light, and then use a cheap battery to store the energy,” Wu said. “We’ve integrated both functions into one device. Any time you can do that, you reduce cost.”

He and his students believe that their device brings down costs by 25 percent.

Researchers at The Ohio State University have invented a solar battery — a combination solar cell and battery — which recharges itself using air and light. The design required a solar panel which captured light, but admitted air to the battery. Here, scanning electron microscope images show the solution: nanometer-sized rods of titanium dioxide (larger image) which cover the surface of a piece of titanium gauze (inset). The holes in the gauze are approximately 200 micrometers across, allowing air to enter the battery while the rods gather light. Image courtesy of Yiying Wu, The Ohio State University. 

The invention also solves a longstanding problem in solar energy efficiency, by eliminating the loss of electricity that normally occurs when electrons have to travel between a solar cell and an external battery. Typically, only 80 percent of electrons emerging from a solar cell make it into a battery.

With this new design, light is converted to electrons inside the battery, so nearly 100 percent of the electrons are saved.

The design takes some cues from a battery previously developed by Wu and doctoral student Xiaodi Ren. They invented a high-efficiency air-powered battery that discharges by chemically reacting potassium with oxygen. The design won the $100,000 clean energy prize from the U.S. Department of Energy in 2014, and the researchers formed a technology spinoff called KAir Energy Systems, LLC to develop it.

“Basically, it’s a breathing battery,” Wu said. “It breathes in air when it discharges, and breathes out when it charges.”

For this new study, the researchers wanted to combine a solar panel with a battery similar to the KAir. The challenge was that solar cells are normally made of solid semiconductor panels, which would block air from entering the battery.

Doctoral student Mingzhe Yu designed a permeable mesh solar panel from titanium gauze, a flexible fabric upon which he grew vertical rods of titanium dioxide like blades of grass. Air passes freely through the gauze while the rods capture sunlight.

Normally, connecting a solar cell to a battery would require the use of four electrodes, the researchers explained. Their hybrid design uses only three.

The mesh solar panel forms the first electrode. Beneath, the researchers placed a thin sheet of porous carbon (the second electrode) and a lithium plate (the third electrode). Between the electrodes, they sandwiched layers of electrolyte to carry electrons back and forth.

Here’s how the solar battery works: during charging, light hits the mesh solar panel and creates electrons. Inside the battery, electrons are involved in the chemical decomposition of lithium peroxide into lithium ions and oxygen. The oxygen is released into the air, and the lithium ions are stored in the battery as lithium metal after capturing the electrons.

When the battery discharges, it chemically consumes oxygen from the air to re-form the lithium peroxide.

An iodide additive in the electrolyte acts as a “shuttle” that carries electrons, and transports them between the battery electrode and the mesh solar panel. The use of the additive represents a distinct approach on improving the battery performance and efficiency, the team said.

The mesh belongs to a class of devices called dye-sensitized solar cells, because the researchers used a red dye to tune the wavelength of light it captures.

In tests, they charged and discharged the battery repeatedly, while doctoral student Lu Ma used X-ray photoelectron spectroscopy to analyze how well the electrode materials survived — an indication of battery life.

First they used a ruthenium compound as the red dye, but since the dye was consumed in the light capture, the battery ran out of dye after eight hours of charging and discharging — too short a lifetime. So they turned to a dark red semiconductor that wouldn’t be consumed: hematite, or iron oxide — more commonly called rust.

Coating the mesh with rust enabled the battery to charge from sunlight while retaining its red color. Based on early tests, Wu and his team think that the solar battery’s lifetime will be comparable to rechargeable batteries already on the market.

The U.S. Department of Energy funds this project, which will continue as the researchers explore ways to enhance the solar battery’s performance with new materials.

How to Make a “Perfect” Solar Absorber

Cambridge, Mass. -- The key to creating a material that would be ideal for converting solar energy to heat is tuning the material’s spectrum of absorption just right: It should absorb virtually all wavelengths of light that reach Earth’s surface from the sun — but not much of the rest of the spectrum, since that would increase the energy that is reradiated by the material, and thus lost to the conversion process.

This rendering shows the metallic dielectric photonic crystal that stores solar energy as heat. Credit: Jeffrey Chou

Now researchers at MIT say they have accomplished the development of a material that comes very close to the “ideal” for solar absorption. The material is a two-dimensional metallic dielectric photonic crystal, and has the additional benefits of absorbing sunlight from a wide range of angles and withstanding extremely high temperatures. Perhaps most importantly, the material can also be made cheaply at large scales.

The creation of this material is described in a paper published in the journal Advanced Materials, co-authored by MIT postdoc Jeffrey Chou, professors Marin Soljacic, Nicholas Fang, Evelyn Wang, and Sang-Gook Kim, and five others.

The material works as part of a solar-thermophotovoltaic (STPV) device: The sunlight’s energy is first converted to heat, which then causes the material to glow, emitting light that can, in turn, be converted to an electric current.

Some members of the team worked on an earlier STPV device that took the form of hollow cavities, explains Chou, of MIT’s Department of Mechanical Engineering, who is the paper’s lead author. “They were empty, there was air inside,” he says. “No one had tried putting a dielectric material inside, so we tried that and saw some interesting properties.”

When harnessing solar energy, “you want to trap it and keep it there,” Chou says; getting just the right spectrum of both absorption and emission is essential to efficient STPV performance.

Most of the sun’s energy reaches us within a specific band of wavelengths, Chou explains, ranging from the ultraviolet through visible light and into the near-infrared. “It’s a very specific window that you want to absorb in,” he says. “We built this structure, and found that it had a very good absorption spectrum, just what we wanted.”

In addition, the absorption characteristics can be controlled with great precision: The material is made from a collection of nanocavities, and “you can tune the absorption just by changing the size of the nanocavities,” Chou says.

Another key characteristic of the new material, Chou says, is that it is well matched to existing manufacturing technology. “This is the first-ever device of this kind that can be fabricated with a method based on current … techniques, which means it’s able to be manufactured on silicon wafer scales,” Chou says — up to 12 inches on a side. Earlier lab demonstrations of similar systems could only produce devices a few centimeters on a side with expensive metal substrates, so were not suitable for scaling up to commercial production, he says.

In order to take maximum advantage of systems that concentrate sunlight using mirrors, the material must be capable of surviving unscathed under very high temperatures, Chou says. The new material has already demonstrated that it can endure a temperature of 1,000 degrees Celsius (1,832 degrees Fahrenheit) for a period of 24 hours without severe degradation.

And since the new material can absorb sunlight efficiently from a wide range of angles, Chou says, “we don’t really need solar trackers” — which would add greatly to the complexity and expense of a solar power system.

“This is the first device that is able to do all these things at the same time,” Chou says. “It has all these ideal properties.”

While the team has demonstrated working devices using a formulation that includes a relatively expensive metal, ruthenium, “we’re very flexible about materials,” Chou says. “In theory, you could use any metal that can survive these high temperatures.”

“This work shows the potential of both photonic engineering and materials science to advance solar energy harvesting,” says Paul Braun, a professor of materials science and engineering at the University of Illinois at Urbana-Champaign, who was not involved in this research. “In this paper, the authors demonstrated, in a system designed to withstand high temperatures, the engineering of the optical properties of a potential solar thermo photovoltaic absorber to match the sun’s spectrum. Of course much work remains to realize a practical solar cell, however, the work here is one of the most important steps in that process.”

The group is now working to optimize the system with alternative metals. Chou expects the system could be developed into a commercially viable product within five years. He is working with Kim on applications from this project.

The team also included MIT research scientist Ivan Celanovic and former graduate students Yi Yeng, Yoonkyung Lee, Andrej Lenert, and Veronika Rinnerbauer. The work was supported by the Solid-State Solar Thermal Energy Conversion Center and the U.S. Department of Energy.