Solar Heating Panels on the White House Roof

Still under the impression of the USA 2008 Presidential vote (although I am not an American) I found this information interesting to be published now.

Did you know that way back in 1979 (during the second US oil crisis) the American President Jimmy Carter installed solar heating panels on the roof of the White House West Wing? I personally didn't know that curious fact! And it seems that the Nobel Prize winning President Carter was quite a visionary.

In July 1979, President Carter outlined his plan for achieving energy independence and improving energy efficiency in his "Crisis of Confidence" speech. In an effort to set an example for the nation, he installed solar panels on the White House roof. They were more as a symbol of a new strategy to reduce America’s dependence of foreign sources of energy and a move designed to support Carter’s solar institute, which he had “created to spearhead solar innovation.”

Carter called for 20 percent of American energy to come from solar power by the year 2000. He even had very generous tax reductions implemented for people who installed solar panels at home.

The solar-energy system that President Carter installed consisted of 34 solar collectors which were used to heat water for the staff eating area and some other areas of the White House.

At the time, President Carter warned "a generation from now, this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be a small part of one of the greatest and most exciting adventures ever undertaken by the American people; harnessing the power of the Sun to enrich our lives as we move away from our crippling dependence on foreign oil." (It turns out Carter's warning was at least partially correct: One of his solar panels is now museum piece.)

In 1986, President Reagan had the solar panels removed during a roof in repair and put them into a federal storage facility. Actually, the solar panels were supposed to be reinstalled but they never were.

In 1991, the environmentally-minded Unity College of Maine, found the panels in a government warehouse in Franconia, Va., bought them for peanuts and installed them to use for the generation of hot water in the student dining hall.

By 2004, the solar panels had worn out. Unity College kept one of the panels for “historical significance,” donated another panel to the Smithsonian Institute and offered the rest for sale.

Even a documentary film has been made about the solar panels, using them as a backdrop to explore American oil dependency and the political lack of will to pursue alternative energy. Swiss directors Christina Hemaner and Roman Keller follow the route of the panels in the hour-long film "A Road Not Taken."

In 2003, the National Park Service, which manages the White House complex, installed a nine kilowatt solar electric or photovoltaic panels, on the roof of the main building used for White House grounds maintenance. Solar thermal systems were also installed to heat water: one for landscape maintenance personnel, the other for the presidential pool and spa.

China - a World Leader in the Solar Water Heating Market

A roof-mounted solar water heater
Photo credit: www.bcsea.org

China is by far the world's largest producer and consumer of solar water heaters. A basic models of solar water heaters in China are very cheap, starting at around 1,500 yuan (US$190). By 2006, the cumulative installed area of water heating collectors in China hit 100 million square meters, and that is roughly 80 percent of the global solar thermal capacity installed worldwide. But this number corresponds only to 78 sqm of collector surface installed for every 1000 inhabitants, which implies a large margin of market potential. So, although China is the biggest solar thermal producer and market in the world, per capita installations of solar hot water systems are still quite low compared to countries like Israel, Greece, Cyprus, Germany and many others.

More than 30 million Chinese households now have one solar water heater installed, and the popularity is due to the efficient evacuated tubes which allow the heaters to function even under cloudy or smog-choked skies and at temperatures well below freezing. The evacuated tube technology was initially developed by Qing Hua University in Beijing in the early eighties, with pilot manufacturing in 1985.

A report from the China's top planning authority predicted that by 2010, the coverage of solar water heating systems in operation in China will reach 150 million square meters. It is also estimated, that by utilizing solar energy, China can save more than 50 million tons of coal in 2010.

Going Green with a Solar Water Heater

Utilizing energy of the sun to heat water is one of the oldest forms of solar technology available. The first commercial solar hot water heater was patented by Baltimore inventor Clarence Kemp in 1891 (he called his solar water heater the Climax), and since then improvements in performance, design, and level of complexity have made solar water heaters the perfect choice for homeowners looking to go green and create more sustainable home.

There are several different types solar water heaters, including those with pumps and those that work passively. Basically, solar water heating systems have two main parts: a hot water storage tank and some type of collector that absorbs solar energy. The most modern solar water heaters mount flush with a home's roof and resemble skylights. Geographic location, collector orientation, and collector size will determine how much energy can be provided for domestic hot water heating.

On an average single-family residence, there will typically be one or two solar collector panels on the roof. Some homeowners use the solar water heating system exclusively (sometimes with a gas or electric tankless water heater as a backup energy source), while others pair them with other systems as pre-heaters.

Solar water heating systems cost depends on a number of factors, such as the size of the system and the particular system manufacturer, the number of people in the household, the current hot water usage, the type of roof it is going to sit on, trees causing shadows, etc. The typical solar heating system costs in the range of $2,000 - $6,000. Any solar rebates and other incentives available in your area will reduce the total cost. You can find more detailed information about it at www.dsireusa.org (for USA customers).

Using solar energy to meet part or all of your home's domestic hot water needs have a good economic payoff and can be a valuable and cost effective option to invest. When correctly installed, a solar hot water system can reduce your water-heating bills 50-80%, depending upon water consumption. With a solar water heating system, you'll get the hot water your household needs, save electricity which means saving money, reduce your dependence on coal-fired power and benefit the environment. Saving electricity means reducing emissions created by burning fossil fuels and water consumption at power stations, thus taking steps to save the environment. When a water heating system is combined with an electric water heater, pollutant emissions are reduced by about 2,800 pounds per year. A solar system replacing natural gas will reduce pollution by 1,200 to 1,600 pounds annually.

Solar water heaters pay for themselves in four to eight years and should function for 20+ years.

Active Solar Heating

Diagram of a house with a combined solar domestic hot water and space heating system ("combisystem") (www.estif.org)

Active solar energy is more complex and requires mechanical devices to capture, store and convert the solar power into other useful forms of energy.

Active solar heating generates much more heat than passive systems do. Active solar heating relies strongly on three components: a solar collector to absorb the solar energy, a solar storage system, and a heat transfer system to disperse the heat to the appropriate places in your home. Liquid-based heating systems use a liquid to collect the energy in the solar collector; whereas air-based heating systems absorb the energy through the air.

Active solar technologies are used to convert solar energy into useable heat and cause air movement for ventilation or cooling.

Passive Solar Space Heating

Picture: westernwashingtonsolar.com

Space heating means heating the space inside a building. Passive solar space heating relies on incorporating building features that absorb heat and then release it slowly to maintain the temperature within the home. These building features, known as thermal mass, may include large windows, brick walls, and stone flooring. Passive solar heating techniques generally fall into one of three categories: direct gain, indirect gain, and isolated gain.

Direct gain is solar radiation that directly passes through the home's windows and is traped in the living space. Direct gain uses classic passive solar design strategy - the sunlight falls directly into the space and is absorbed by an abundance of thermal mass materials.

Indirect gain collects, stores, and distributes solar radiation using some thermal storage material (e.g., Trombé wall or a thermal storage wall). Conduction, radiation, or convection then transfers the energy indoors. Sunlight is absorbed by the wall, which heats up slowly during the day. Then as it cools gradually during the night, it releases its stored heat over a relatively long period of time indirectly into the space.

Isolated gain (e.g., sunspace) collect solar radiation in an area that can be selectively closed off or opened to the rest of the building. That heat than can be distributed into the living area in a variety of ways. The sunspace has the same characteristics as a direct-gain system - extensive south-facing glazing and thermal mass, and it should be well constructed, with low infiltration and high insulation levels.

In the case of passive solar space heating the whole house operates as a solar collector (passive solar home). A passive solar home is designed to let in as much sunlight as possible. It is like a big solar collector.

Sometimes for passive solar energy to be utilized effectively there must also be a means for the heated air to circulate throughout the home. Usually, the natural circulation of air is enough as long as doors are left open throughout the home, however, sometimes fans are also incorporated into the design to facilitate this.

Passive solar heating features can reduce heating bills by almost 50 percent and it requires little or no investment of external equipment. Building a passive solar home may even cost the same as building a conventional home, especially if you're working with a builder who is familiar with the processes of passive solar heating systems.

Solar Heating Systems

Solar heating can be used to heat the space in homes and buildings or to heat the water. There are two basic types of solar heating systems: passive solar heating and active solar heating.

The appropriate use of windows along with building design is called passive solar heating. The buildings can be designed to make the best use of the sun in winter while keeping the heat out in summer. South-facing, large windows, building materials that absorb and retain heat (such as stones and bricks), and efficient airflow are among the design features of a home that takes advantage of passive solar.

Active solar heating systems use mechanical equipment, such as pumps and fans, to increase the usable heat in a system. The heat is primarily used for heating water in homes, commercial buildings and industrial facilities. Active solar heating can be further divaded into liquid-based and air-based systems according to the kind of energy transfer fluid that is used.