Climate-Friendly Agriculture and Renewable Energy: Working Hand-in-Hand toward Climate Mitigation

By Laura Reynolds and Sophie Wenzlau, Worldwatch Institute
December 21, 2012 | 

Worldwide, agriculture contributes between 14 and 30 percent of human-caused greenhouse gas (GHG) emissions because of its heavy land, water, and energy use—that’s more than every car, train, and plane in the global transportation sector. Livestock production alone contributes around 18 percent of global emissions, including 9 percent of carbon dioxide, 35 percent of methane, and 65 percent of nitrous oxide.

Activities like running fuel-powered farm equipment, pumping water for irrigation, raising dense populations of livestock in indoor facilities, and applying nitrogen-rich fertilizers all contribute to agriculture’s high GHG footprint.

The good news? The UN Food and Agriculture Organization (FAO) estimates that the sector has “significant” potential to reduce its emissions, including removing 80 to 88 percent of the carbon dioxide that it currently produces.

Some of this reduction can be achieved by substituting renewable energy for the fossil fuels typically used to power day-to-day farm activities. Do-it-yourself solar heat collectors can warm livestock buildings, greenhouses, and homes; small or cooperatively owned wind and water turbines can pump water and power equipment; photovoltaic panels can power critical farm operations like electric fencing and drip irrigation systems; and designing or renovating buildings and barns to maximize natural daylight can dramatically reduce the electricity required to light and warm farm buildings.

These innovations can be scaled up for implementation on large farms, but their beauty is in their simplicity, accessibility, and application to the smallest of operations.

And greening a farm does not stop at replacing fossil fuels with renewable energy. To make a farm truly climate-smart, it must take into account all aspects of its environmental footprint: soil fertility, water use, chemical inputs, and biodiversity. Farmers can implement low-tech, low-cost practices to curb their emissions while building resilience to weather shocks and severe resource scarcity, two projected stumbling blocks for farmers in coming decades.

Any measure that reduces on-farm water use, for instance, will help to relieve the heavy pressures on the planet’s dwindling resources while reducing agriculture’s energy footprint. Agriculture accounts for a whopping 70 percent of global water use; in the United States, the figure rises to 80 percent. Rivers, lakes, and underwater aquifers are drying up across the globe, causing serious concerns over basic human rights like sanitation, food production, and safe drinking water.

Installing drip irrigation, which applies precise amounts of water to the plant roots instead of spraying water over plants, is a simple way to invest in climate-stress mitigation. Watering crops using “greywater,” or water used in domestic activities like dishwashing, laundry, and bathing — not to be confused with blackwater, or sewage — can also reduce water use on farms, particularly small-scale operations. And switching from “thirsty” crops like rice, wheat, and sugarcane (which account for nearly 60 percent of the world’s irrigated cropland) to less-demanding plants like sorghum, millet, lettuce, broccoli, carrots, beans, and squash can reduce on-farm water use and help farmers cope with drought and other threats (while broadening access to fresh and nutritious foods).

Water conservation is just one approach to making a farm more climate-friendly. Practices such as using animal manure rather than artificial fertilizer, planting trees on farms to reduce soil erosion and sequester carbon, and growing food in cities all hold huge potential for reducing agriculture’s environmental footprint.

Interestingly, biofuels can combine the need for renewable energy with climate-friendly agricultural practices.

Perennial bioenergy crops stand as a shining example of agricultural innovation. While corn has long reigned the biofuels industry, its relative energy-conversion inefficiency and its sensitivity to high temperatures make it an unsustainable long-term energy option. But trees and shrubs like willow, sycamore, sweetgum, and cottonwood offer promising alternatives. These perennials grow quickly for many years, can often thrive on marginal land, and are often much hardier than annual plants like corn or soybeans. Their long roots can also reduce erosion, filter groundwater, harbor beneficial microorganisms, and help soil retain key nutrients like phosphorus and nitrogen.

Because we may need to double our global food production by 2050 to feed the projected world population, it is important that farmers do not divert their food-bearing land to grow energy crops. Although corn- and soy-based biofuels must be produced on fertile agricultural land, perennial crops can often thrive on marginal land (i.e. steep slopes and eroded soil) that would otherwise fallow. In the United States, 27 million acres are currently enrolled in the U.S. Department of Agriculture’s Conservation Reserve Program, which pays agricultural landowners to grow long-term, resource-conserving cover crops on their marginal or unused farmland. A portion of this program’s enrolled land could be planted with perennial crops and harvested regularly for fuel production.

And because perennial crops require considerably less fertilizer, pesticides, and herbicides — not to mention time and labor — than annual crops, they are a natural choice for the millions of farmers around the world who cannot access or afford expensive chemical inputs.

By tapping into the multitude of climate-friendly farming practices that already exist, agriculture can continue to supply food for the world’s population, and also help to reduce our dependence on fossil fuels. But if we want agriculture to contribute to climate change mitigation, climate-friendly food production will need to receive increased attention — in the form of both research and investment — in the coming years.

A step in the right direction: in early December, a presidential advisory council on science and technology warned that U.S. agricultural research has not prepared the country for the predicted impacts of climate change, population growth, emerging pests and diseases, and severe resource depletion and scarcity. The United States and other countries must promote innovative agricultural research to brace for these serious challenges, and to protect the livelihoods of the 1.3 billion people whose livelihoods rely on agriculture.

Laura Reynolds and Sophie Wenzlau are Staff Researchers for the Food and Agriculture Program at the Worldwatch Institute. Laura co-authored Innovations in Sustainable Agriculture: Supporting Climate-Friendly Food Production, which was released earlier this month.
Bioenergy, Solar Energy, Wind Power

The information and views expressed in this article are those of the author and not necessarily those of RenewableEnergyWorld.com or the companies that advertise on its Web site and other publications.

Solar Windows

If you picture the glittering glass skyscrapers that dot America’s cities, it becomes clear why the idea of using that vast window space to generate solar power is gaining traction. In 2009 alone, 437 million square feet of windows were installed in non-residential buildings in the United States. That many square feet of standard solar panels would generate around 4 gigawatts of power, roughly the total installed solar capacity in the U.S. today.

Such potential is leading engineers and entrepreneurs to more intensively explore the idea of turning windows into solar-power producers. Solar windows, a subset of the growing field known as building-integrated photovoltaics, are based on the concept that a window doesn’t need to be 100 percent transparent, and a solar panel doesn’t need to be 100 percent opaque. Several ways currently exist to turn a window into a power-generating device, from thin-film silicon, to dye-sensitized solar cells, to tiny organic cells.

New Energy SolarWindow

Some experts think the field is poised to take off, and although the world may not see an all-solar skyscraper for a while, a number of companies are promising commercial-scale production of various solar windows in the next two years. Still, the cost and technical hurdles facing this fledgling technology could get in the way of a future filled with towering, emission-free power plants. Like other cutting edge alternative energy sources, energy-generating windows could become a mainstay of a greener future in the coming decades, or they could prove to be impractical and produce only a fraction of solar-powered electricity.

“The challenge is whether you can get the cost down and the electricity generation up,” says Sarah Kurtz, a scientist with the U.S. government’s National Renewable Energy Laboratory (NREL) in Colorado. “There are lots of different schemes and strategies, and creativity will be the name of the game. If you can get the cost to the place where those windows don’t really cost any more than conventional windows, it obviously makes sense to go ahead and have your windows generate electricity.”

Building-integrated photovoltaics, or BIPV, is moving slowly, with solar panels now doubling as walls, shingles, and other parts of buildings. MJ Shiao, a senior analyst at GTM Research, a market analysis group in Cambridge, Massachusetts, says the market still represents only around 1 percent (a few hundred megawatts last year) of solar powerbeing installed around the world, and that’s mostly rooftops or semi-opaque skylights. Windows pose a greater challenge than rooftops or walls because of the need to actually see through them. So far, very few examples of skyscrapers with solar windows exist; the highest profile site is the Willis Tower (formerly Sears Tower) in Chicago, where Pythagoras Solar installed a small prototype in 2011.

Several technologies have emerged for solar windows, though none have yet taken off in a meaningful way. But one company that says it is close to commercial deployment is New Energy Technologies, based in Columbia, Maryland. It has developed a method for spraying tiny organic solar cells onto windows in a see-through coating that lets in 40 to 80 percent of sunlight, absorbing the rest. With 10 patent filings pending and no commercial prototypes yet in the field, the company is divulging few details. But the spray-on method could reduce production costs dramatically. Recently, the company announced the development of a large solar cell — 170 square centimeters — made in collaboration with NREL, which could make adding the cells to windows even cheaper.
Despite the company’s progress, its technologies highlight one of the major obstacles to solar windows: efficiency. The rate at which a solar panel turns the sun’s energy into electricity is a concern for all types of solar power, but especially for windows. “The challenge is that the light you see, if you absorb that and use it to make electricity, that means you don’t have a window anymore,” says Kurtz.

To date, the record efficiency for an organic solar cell is 10 percent, and production line efficiencies never get up to the record levels. While traditional solar panels are now producing power with 15 to 20 percent efficiency, efficiency levels for solar windows of roughly 5 percent are unlikely to be economical.

“Look at it from a physicist’s point of view,” Kurtz says. “A solar panel that’s put out in the desert in a nice location with lots of sunshine may have something on the order of a one-year payback. If that [panel] sits out there for another 20 years, you get that much return on your investment for society.” If a solar window can only achieve one-third the efficiency of a solar panel, then it will take three times as long to pay back the investment.

But some experts think it’s just a matter of time before efficiencies rise high enough — and costs drop low enough — to make solar windows a sound investment. Andreas Athienitis, a professor of mechanical engineering at Concordia University in Montreal who is working on technologies for solar windows, says more mature technologies like thin-film silicon might represent a short- and mid-term solution for BIPV, until organic cells can catch up and meet long-term goals. “I think eventually it will be a big market,” he says, but the adoption is slow because “it’s a disruptive technology.”

organic-valley-solar-windows

Another company using organic solar cells, Heliatek, based in Germany, has panels that can achieve 8 percent efficiency. The company’s organic cells use molecules called oligomers rather than traditionally used polymers — basically, short rather than long collections of atoms — which means cheaper, more precise application of the cells. Heliatek says it expects that within five years it can manufacture solar cell windows in the 50 cents-per-watt range, making them competitive with other solar technology.

Spain-based Onyx Solar offers a number of solar glass technologies. However, its windows only allow up to 30 percent of sunlight through, so a lot of light inside the building is lost. In varying formations, though, Onyx says its amorphous-silicon solar glass — a type of thin-film silicon cell — can get up to 9-percent efficiency.

But such efficiencies don’t take into account some of the practical limitations of actually covering a skyscraper with solar windows.

“The optimal installation for solar is you want it to be facing south, you want a slight tilt to it, and you want good solar access, so you don’t want anything to shade those panels,” says Shiao, of GTM Research. “The problem with skyscrapers is suddenly you’re putting them in vertical orientation, there’s only one south side to the building, and chances are that skyscraper is next to another skyscraper, which is going to shade that side of the building.”

Such challenges have left Shiao and other experts skeptical that solar windows will have a bright future. “There are a lot of technical and design challenges, which quite honestly aren’t going to be fixed,” Shiao says. “It doesn’t make sense almost at any cost, unless you’re getting the panels for free or something, to really install that system on those big structures.”

These obstacles haven’t deterred numerous fledgling companies. Oxford Photovoltaics, spun out of research done at Oxford University, says that computer modeling of a 700-foot skyscraper in Texas suggests thatcovering it in solar windows would generate up to 5.3 megawatt-hours per day of electricity. That’s enough to power 165 homes, and it could provide a skyscraper with sufficient power for all its lighting.

Oxford’s technology involves a type of cell for solar windows called a dye-sensitized solar cell. Dye-sensitized cells use a photo-electrochemical process to generate power and can be made relatively cheaply. Oxford’s transparent panels are so far getting around 6 percent efficiency, and the company hopes to bring them to market late next year.

Nazir Kherani, a professor of engineering at the University of Toronto, believes that the economics of solar windows may be most compelling for new construction with a focus on net-zero energy buildings — not for retrofitting existing skyscrapers. “With sufficient attention to design and seamless engineering, it is conceivable that we may see such buildings gradually evolving into net-zero communities, villages, and towns,” Kherani says.

Several companies involved in solar window production say they are within a year or two of scaling up or bringing a product to market, and they maintain that cell efficiencies will continue to rise and prices continue to fall, as is the case with solar panels.

What continues to drive the inventors and entrepreneurs involved in developing solar windows is the enormous potential for energy savings. Buildings accounted for 41 percent of all electricity consumption in the U.S. in 2010, more than transportation or industry. Taking a bite out of that with power-generating windows is an alluring target.

“I wouldn’t write off the possibility,” Kurtz says. “How soon will it happen? I find it’s really dangerous to predict the future.”

source :http://www.earthtechling.com/2012/05/will-solar-windows-transform-buildings-to-energy-producers/

The Sun Rises on Solar Power



The Sun Rises on Solar Power -- Ford Focus Electric -- © Westend61/SuperStock
by Denise DiFulco
The price of solar electric systems has fallen rapidly in recent years, making solar energy more accessible than ever. In 2010, the installed cost of residential and commercial solar photovoltaic power systems fell by 17 percent from the previous year, falling an additional 11 percent in the first half of 2011, according to a report by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). So is now the time to take the plunge?
Well, such statistics don’t mean that solar power systems are cheap. The average cost nationwide last year was $6.20 per watt, says Ryan Wiser, a Berkeley Lab scientist. An average-size home (about 2,000 square feet) generally requires a 5-kilowatt system — approximately a $31,000 investment. “There’s a large up-front cost, but there’s also economies of scale,” Wiser says. “The cost per unit on a smaller system will be higher.” So if you opt for more power — say, a 10-kilowatt system — the price per watt will be substantially lower. Your circumstances could also help: It’s cheaper to install a system on new construction versus an existing home. There are several ways to defray the overall costs. One is through state and federal solar energy rebates. A list of current rebates is available through theDatabase of State Incentives for Renewables and Efficiency. Another is by entering a net metering agreement with your utility company. When your system generates more power than you need, the excess returns to the electricity grid and your meter runs backward. This allows you to receive full retail credit for the power your system generates. A way to avoid up-front costs altogether is to lease. Leasing has become a popular option in recent years, Wiser says, with more than half of new installed systems being leased through companies such as SolarCity, SunRun and Sungevity. How much you can potentially save on electricity depends upon many factors, including the size of the system you choose and your current retail electricity rate. Online calculators, such as Berkeley Lab’s Home Energy Saver, can help you make that determination. They also can help assess other ways to make your home more energy efficient, which is the best first step to take when switching to solar power. “We tell people they really need to look at their building energy use,” says Sherri Shields, a spokeswoman for the Florida Solar Energy Center, a research institute of the University of Central Florida. “The more energy efficient you make your home, the less equipment you need to put on your roof.” If you’re purchasing your own solar panels, as opposed to leasing, it’s best to hire a local solar contractor or an electrical contractor that specializes in solar power. The contractor will take into account many considerations, including how much energy your home uses and potential sites for the panels. The type of roof you have, which direction your home faces and even nearby trees and other shade-producing obstructions all need to be factored in as well when designing a system. “It’s not just something cookie-cutter, out of the box,” Shields explains. Other things to keep in mind? Check with your insurance company to make sure your system will be covered under your homeowners insurance. Sometimes, a separate rider to the policy is required. Also, be sure all components carry the Underwriters Laboratories (UL) mark for quality and safety, and inquire about a truss-mounted system for roof panels — especially if you live in an area prone to severe weather. “We have to be especially careful in Florida,” Shields says. “If it’s not part of the roof structure, it’s going to come falling off.” Still in need of more information? A good basic guide for getting started is also available here, through the U.S. Department of Energy’s National Renewable Energy Laboratory. So put your plan together, go solar, and expect many sunny days in your future.