I’ve always wanted a solar water heater in my imaginary house that I own, and now I think I know what brand I want, too. EnerWorks solar water heaters are the first to qualify for the new ENERGY STAR residential water heater program. The heaters were judged based on numerous factors, including solar fraction (portion of hot water delivered by solar energy), solar energy factor (energy delivered by the system divided by electrical or gas energy put into the system), and warranty.

Read more of this story »

When you are in the shower, the hot water from the shower strikes your body and transfers some heat before it falls away. But most of the heat in that water simply goes down the drain. Reportedly, 80 to 90 percent of the energy used to heat water for the shower is lost down the drain.

A drain water heat recovery unit (DWHR) transfers heat from water running down the drain to cold water going to the water heater. This preheats the water so that the heater is starting with warmer water, and thus needs less energy. A DWHR unit can save as much as 25-30% of the energy used for water heating, and payback periods range from 3 to 7 years, depending on use patterns.

Read more of this story »

Each week, the Chicago Architecture Foundation and Chicago Green Technology Center graciously host “lunch time seminars,” inviting some of the leading industry professionals to discuss building issues they are involved with. On 5/1/08, they hosted Joe Gordon’s “Solar Hot Water and Heating- Is It Right for You?” presentation. The seminar provided the audience with information on how solar thermal works, how much space you’ll need, incentives, and how to determine cost benefits. Mr. Gordon also discussed how the cost of solar hot water and heating will likely keep increasing, due to the high cost of copper that is used in these systems.

Joe Gordon has worked for Solar Service, Inc. for over four years and has fielded thousands of inquires from developers, architects, owners and institutions about whether solar hot water and heating would work for them. Visit Solar Service’s gallery to see unique ways panels can be installed.

This story contains additional media. Click here to view the media.

Read more of this story »

Using only water-filled beer bottles and connecting hoses, Ma’s mother now has hot water on demand, and so do more than 20 other families in the village whom Ma has helped build their own system.

He wants to build a public bathroom for the village using the same process, but he needs enough money to buy the beers. He probably has plenty of volunteers to empty them.

Image and source.

The 20 teams selected for the 2009 Solar Decathlon have been announced by the US Department of Energy. Each team will receive a $100,000 grant from the DOE to be used for creating a completely solar-powered home for the competition.

The full list can be found in an article at Custom Home Online. The 2009 competition has some international flavor, including last year’s winner, the Technische Universität Darmstadt, as well as the Universidad Polytécnica de Madrid and two groupings of Canadian universities.

• » See also: Volunteer at 1bog.org to help educate about solar energy
• » Get Green Building Elements by RSS or sign up by email.

One former faculty adviser to a university Decathlon team lamented the reduction of the Solar Decathlon to a more narrow range of design concepts. The first few Decathlons were wide-open events, with very different designs. But with certain criteria in place, the strategies have been narrowed down to address the specific problems posed by the Decathlon challenge. These are still good designs that are being produced, but they are now tuned to a set of particular requirements and criteria.

Homes designed for the Decathlon should perhaps be viewed in the same spirit as one views Formula One race cars compared to ordinary cars. In the cases of both the auto race and the Solar Decathlon, the competitors are tuned for specific ways of maximizing the allowable methods for winning a contest. While some developments in the competition may trickle down to more prosaic, domestic uses, it’s not a representative testbed.

We’ll certainly be looking at the entries when the Decathlon is held; however, I don’t expect to see great numbers of them making an appearance in a neighborhood anytime soon. Like race cars, they are great to look at, and fun to think about using, but for most of us, they aren’t a practical alternative to what we have now.
Image (Kansas State/Univ. Kansas 2007 entry in front of Washington Monument) via Curious Cat

“Homeowners will have to use renewable energy sources to meet 14% of a household’s total energy consumption for heating and domestic hot water,” starting in 2009.

Image credit: Dave Yoder for The New York Times

Evacuated tube heaters are another method of collecting solar energy. Rather than running the water through a long circuitous course, each tube is a separate heat collector. It is made of a clear glass cylinder which allows sunlight to pass through, and a central heat collector tube. The evacuated tube insulates the collector element, which makes it more efficient in colder environments. The collector itself is typically filled with an antifreeze mix rather than just water. The top of the tube has a heat exchange element which is prevents contamination of the water being heated. The tubes are collected together in an array, with a manifold across the tops, containing the heat exchangers.

Image credit: Enviro-friendly.comEvacuated tube collectors are more efficent than water circulating collectors, and can reach higher temperatures, especially in wintertime. Because of their greater efficiency, a water heating system using evacuated tube solar collectors will generally be smaller than a comparable water circulating assembly. The cylindrical form of the tubes also means that the collectors are always perpindicular to the sun, while flat collectors lose more efficiency early in the morning and late in the afternoon unless they are rotated to track the sun (see diagram). Evacuated tube systems can also be easier to operate in a cold environment where concerns about the system freezing at night, particularly during cold winter months, is an issue.

Evacuated tube collectors also help to minimize maintenance. The collectors themselves are sealed, and the water system only has brief contact with the heat exchangers in the manifold. In the event of damage, individual tubes can be fairly readily swapped out, whereas holes in tubing and broken glass over a flat array can be harder and more expensive to repair.

There are a few tradeoffs with evacuated tube collectors. They tend to be more expensive. They can be broken (by hail or falling branches from nearby trees), which looses the vacuum and the efficiency of the tube, and necessitates eventual replacement. They are also sometimes unsuitable for snowy climates, as well, because the heat gathering element is insulated with a vacuum which means that the tubes themselves will stay cool, and can remain covered with snow instead of melting it off as the collector gets heated up.

In the right location, evacuated tube solar collectors can be a good choice for use in conjunction with a hot water system or a radiant floor system (or both). Any form of solar hot water system has a much shorter payback period than a photovoltaic system, and is well worth considering. Evacuated tube collectors are not as well known, but should be part of that evaluation, as well.

Links:

Silicon Solar

Sunpower Canada

Enviro Friendly Products

Wikipedia