CA urged not to neglect PV's less sexy cousin.

[skids]

Too often neglected in the race for "a million solar roofs" is the less glamorous, but much more cost effective cousin of the PV panel, the solar water heater.

A coalition of policy makers, environmental groups and businesses launched a campaign to expand California's solar power market to include solar water heating, a rooftop technology that captures sunlight to reduce fossil fuel use in homes and businesses.

The group recently released a report by Environment California Research & Policy Center quantifying the benefits solar water heating can bring to California and to call for passage of The Solar Hot Water and Efficiency Act of 2007 (AB 1470), authored by Assemblymember Jared Huffman and sponsored by Environment California.

Environment California Research & Policy Center's new report, "Solar Water Heating: How California Can Reduce Its Dependence on Natural Gas," summarizes the current state of solar water heating technology and outlines the significant benefits of growing the market for these systems in California. Some of the benefits highlighted in Environment California Research & Policy Center's report include greater energy independence, a healthier environment and reduced energy bills.

http://www.renewableenergyaccess.com/rea/news/story?id=48281

Link to report:

http://www.environmentcalifornia.org/reports/energy/energy-program-reports/solar-water-heating-how-california-can-reduce-its-dependence-on-natural-gas

...and a few select bullet points from the summary:

* Solar collectors, usually placed on the roof of a home or business, absorb the sun's energy to heat water that is then stored in a water tank. The efficiency of the collectors can be as high as 87 percent, meaning very little solar energy is lost in the process. ed -- currently avaialable PV in contrast is only 10-25% efficient, depending on the type of panel.
* Solar hot water systems in California reduce fuel usage for water heating, usually natural gas, by 75 percent or more in the buildings that employ them. A stronger market for solar hot water systems can reduce California's dependence on natural gas, bring down the price of gas for all con­sumers, and reduce global warming pollution.
* The United States currently has 1.6 GWth of solar hot water capacity installed, or 1.8 percent of global capacity. Hawaii, with a strong re­bate program, installed almost half of the 9,000 new systems in the U.S. in 2006. California, Florida, and Ari­zona each installed about a thousand systems in the same year.

...

* Taking full advantage of solar hot water in California would reduce the state's global warming pollution from water heating by 6.8 million metric tons of carbon dioxide-equivalent per year, as much as the annual emissions of over a million cars. The savings represent about 5 percent of the total reductions needed to meet the state\u2019s global warming pollution cap by 2020.

...

* Fortunately, the market for solar hot water did not collapse in every coun­try, and the technology has contin­ued to improve steadily. As a result, today's solar hot water systems run a net profit for system owners in less than 10 years, but upfront costs and lack of public awareness are barriers to widespread utilization.

This is what you should be doing before even bothering to look at the price of a PV panel.

[Dogmudgeon]

1. Solar thermal can (and does) drive turbines

Solar thermal isn't just for heating water for domestic use. Higher-temporature systems can generate useful electrical power. It is probably (IMO) the best choice for a homebuilt energy system. A trough-shaped collecting mirror eliminates the absolute need for a heliostat (sun-tracking) system. Hooked up to a generator, it can be used to recharge storage batteries.

I am surprised that ST is not more common, especially among "hobbyists".

--p!

[ret5hd]

2. i'd like a link to some info?!!

[skids]

3. links...

Solar thermoelectric is mostly done on an industrial scale:

http://en.wikipedia.org/wiki/Nevada_Solar_One

However, though it is not solar thermoelectric, it is PV with heat recovery, there is this for homes, at least in Canada:

http://www.power-spar.com/Power-Spar/products.php

[jpak]

4. US solar hot water capacity 1.6 GWt - first time I've seen actual numbers for this

:thumbsup:

The OP also implies there are ~98 GWt of solar hot water capacity installed world-wide(????)

That's a lot...

[Maat]

5. Bookmarking.

We are in the midst of planning an environmentally-friendly home. I need all the information I can get my hands on.

[happyslug]

6. Did research on this in the 1970s

Solar Water heaters were big then in areas with NO access to Natural Gas heating (i.e. Southern Florida). Most were home made. That is someone had copper tubing bent into coils under enclosed glass. The Glass turned the light into infrared light, which heat up the Copper panels which ran down to the hot water tank ready for use. The water is pushed to the Panels by Water pressure in the water line itself. This is sometime referred to as an "open" System, for water is always being added and subjected (i.e. used) through the pipes.

In areas where temperatures drop below freezing, the water in the pipes are replaced with glycine which runs to the water tank and heats the water in the tank. The Glycine is a "Closed" System, the Glycine NEVER exits the system, it is just a conduit to heat the water in the Water Tank. You need a pump in such a system to pump the glycine between the panels and the water tank, but you do NOT need to worry about bust water pipes if the water in the pipes would Freeze.

Sellers of Solar Water Panels:
http://www.solarroofs.com/
http://www.solardirect.com/swh/swh.htm
http://www.advancepower.net/
http://www.gaiam.com/realgoods/
http://www.apricus.com/index.htm

Installation of Solar Water heaters is more expensive then installing a Solar Electric Panel, do to the need to run water pipes up to and down from the panels. With Solar Electric Panels all you need is to hook the panel up with your electric Grid.

On the other hand the Solar Water Panels are more efficient AND cheaper if you plan to use Solar power to heat your water.

You can even use the Solar water System to run a Air Conditioner system. There are two different ways to run an Air Conditioner. The first and most Common is Electric compressor system. This method is used on most Refrigerators (and all the Refrigerators I know of made in the last 50 years). The Electric Compression system is simple, the Compressor compresses the Freon (or other refrigerate in the System). As things are compressed, they release heat. The now liquid refrigerate is than run through the back of the Refrigerator (or A/C Unit). Upon reaching the inside of the Refrigerator the refrigerate is permitted to expand, which absorbs heat from the surrounding area. The Freon then returns to the Compressor to be compressed and lose this heat (and the system keeps on going).

In the 1930s and 1940s in addition to the above electric Compression System, you had the the Natural Gas/Absorption system. Such systems are cheaper to run then Electric/Compression systems but are more complex and more expensive to produce. My mother had such a Refrigerator in her home in the late 1940s, but had to give it up when she moved to an area without Natural Gas service. The company that made the Refrigerator had switched to making Huge A/C units in the 1950s and closed in Refrigerator business (people kept buying the cheaper to buy Electric/ Compression system).

For how the Absorption system works see:
http://en.wikipedia.org/wiki/Absorption_refrigeration

Through if you read the paper remember, the Ammonia, Hydrogen and Water are all in a "closed" system. There is NO need to add any of them to the system once made (Unless a leak occurs). Absorption works through the interaction of these three Elements/Compounds.

I bring this up, for the absorption system needs a source of heat. In most cases that was Natural Gas, but you can replace the Heat from Natural Gas by the heat from Hot Water. When I did my research in the 1970s, some people had done so in Florida and other places to keep their electric bills down AND still have A/C.

[NNadir]

7. Glycine?

I think you mean glycol.

Since you were studying these systems thirty years ago, can you offer any insight to why, thirty years later, they aren't more popular?

[skids]

8. I'll offer this insight...

...energy became too cheap to make the products attractive for decades. And besides, we all knew electricity prices were going to go down, down, down, as we entered the bright new "atomic age."

Touche. :-) Not that I acually have the time to fence tonight.

[NNadir]

11. As it happens, only atomic age energy *is* cheap.

The busbar cost of nuclear energy is under 2 cents kw-hr, about less than 1/10 the cost of solar. This explains why nuclear energy produces vast quantities of energy and is the largest form of greenhouse gas free energy there is, about 20% in this country, 16% in the world, and why solar remains a toy for rich kids, usually less than 0.1% Nuclear energy is also more reliable and cleaner.

Solar energy was supposed to be "free." It isn't.

[happyslug]

9. Price, Copper is EXPENSIVE.

The CAPITAL expenditures of these system are high. The Copper pipes must be bent to fit under the glass panel. Water lines must be installed up and down from the Roof (or wherever the location for the Panel is). The system only works when the Sun in up (Thus a larger then normal water tank is needed to store the hot water). Most roofs on homes are NOT strong enough to carry the weight of such panels and the water in the pipes. The need to address the fact water expands when it freezes (i.e. you MUST avoid the pipes freezing, either by draining them when temperatures drop below 32 degrees, Heating the system to prevent Freezing or by making sure the temperature in the area you are installing the panels in rarely if ever below 32 Degrees). Finally the concern someone may build a bigger building between the panel and the sun. blocking the panels, making the whole system less efficient.

The above were enough to get most people to avoid buying Solar Water Heaters, but combined with lack of Knowledge (information was hard to find prior to today's "net age") AND the fact most people would have to have a backup system tended to kill people desire to have a solar Water heater.

Basically, except in areas where the only way to heat water was with Electricity, Solar Water Heaters were viewed as to expensive. There was a push for them in the 1970s, but with the return of cheap Oil and Natural Gas in the 1980s they were forgotten. Surprisingly enough people had faith in them during the 1980s and 1990s for a nice size (but not hugh) industry to be developed. In the 1970s I could find NO ONE who was building Solar Water Panels commercially, most people had build their own. Today you have several sellers of such Panels.

By the way, Jimmy Carter's had Solar Hot Water Panels installed on the White House to heat water for the Showers, Reagan pulled them out.

http://www.businessweek.com/magazine/content/04_36/b3898119_mz018.htm

[Maat]

10. Thanks for the information.

We're weighing it all - Hubby is a chemical engineer; so, that helps.