Slashdot: Hardware's Journal

Could Solar Water Heaters Become Popular Again?
An article in the Washington Post remembers a 1980s-era "glass box with metal water pipes running through it" that "converted sunlight into hot water. By trapping solar energy like a greenhouse, it heated the water to a scorching 180 degrees Fahrenheit. "[T]oday, hardly anyone is using these solar water heaters even as photovoltaic panels have popped up on the roofs of nearly 4 million American homes." Unlike photovoltaic panels, which can power your home, solar thermal panels are mainly used to heat water. But they're smaller and more efficient. The technology converts 60 to 70 percent of the sun's energy into heat. Even the best photovoltaics, which generate electricity, only achieve 24 percent efficiency. Now, a new generation of solar water heater manufacturers is hoping subsidies under the Inflation Reduction Act, and growing interest in net-zero emissions, will reignite their growth. Theoretically, solar thermal offers a big opportunity to slash emissions. Nearly 20 percent of an average home's energy is used to heat water, and nearly 50 percent globally, according to MIT. By adopting solar water heaters, the average household can keep 2 tons of carbon dioxide out of the atmosphere, the equivalent of not driving your car for four months, estimates the Environmental Protection Agency. Solar water heaters can also save money, cutting the average utility bill by $400 to $600 per year, the Energy Department estimates... Only about 370,000 solar thermal systems were operating in the United States by the end of 2021, according to the International Energy Agency, many of them on larger commercial buildings... Since they can cut fuel consumption to heat water by 50 percent to 70 percent, other countries are embracing the technology: Almost all new residential buildings in Israel must include solar thermal, while in countries as far north as Canada and Denmark, solar thermal energy warms millions of homes with district heating systems. Yet these systems represent a tiny fraction of the potential, supplying 0.4 percent of today's global energy demand for domestic hot water. New U.S. subsidies can cut the price in half depending on location, the article points out. Cheap photovoltaics still make economic sense for many homes (unless you're heating a pool). "But the cost of solar thermal could look like a bargain if we consider increasingly unreliable electric grids and the cost to the climate from burning fossil fuels."