What Happens When Solar Power Is as Cheap as Coal

Some observations:

Grid parity is not simply the cost per watt. There are other costs to consider, such as NRE, material costs, and installation costs.

Coal plants are an existing resource that are (in most cases) paid for. At this point of their life cycle there are simply maintenance/operating costs to consider.

Creating a new solar plant not only has the initial material costs and infrastructure costs, but those funds must be borrowed and the payments factored into the cost of doing business. These will be passed onto the end user.

There will also be costs for decommissioning existing coal plants that will, in the end, be passed onto the end user.

Even if Uncle Sam steps in with incentives for private companies to make the switch, those funds come from taxpayer's money. So the end user (and some non-users) still pay more.

The point, the cost parity point between coal and solar is not simply the cost per watt; one must consider the back door costs that such a conversion requires.

Lastly, for many states, reaching output parity to a coal plant will be much more difficult than other states where sunshine is abundant. In sunshine starved states the cost per watt will be higher and necessitate greater energy storage systems to mediate the hours and days where insufficient sunshine is available. Winter hits hard in the northern states and is generally less sunny than Spring and Summer.

I still feel that the solar industry is taking a little too much Prozac right now and while the lowering costs of solar are most welcome, we have a long road to go before we arrive at solar nirvana.

What will happen is obvious. We (humanity) will find a method to consume all the solar power we can produce and still feel the need to have the coal fired plants running.

The paradox will then be the damage done to mine and process the raw materials to build all the additional solar capacity that would be needed.

(However there will be a new business opportunity.) An effective and repeatable way to clean and service the solar collection surfaces (whether mirrors or photocells or whatever) will be the growth sector in the near future. [Just like car detailers and car wash and repair shops developed for the automotive sector.]

What I find ironic is that currently it seems more economic for me to set up a solar system than to build my own "thermal" power plant. In the past it was the huge mechanical systems that were refined and eventually became available for demostic use, (Consider refrigeration plants and pumps) wheras with solar it seems to be the reverse.

Wonder what the hurricane rating is for the collectors.

"Solar power is going to be the wallet-friendly option?"

What is truely amazing is that they will do this without lowering the cost of solar power. "Wallet-friendly" probably won't come to mind when I see my future electric bills.

Robin, I agree that solar water preheaters are the most sensible way to save energy. Do you know any simple designs? I'm going to need one to offset what the carbon tax will do to my electric bills!

"solar water preheaters are the most sensible way to save energy. Do you know any simple designs?"

This has been a recurring discussion here, and a search of the forum site will yield 5 pages of discussions on "Solar Water Heaters". One of the best, in my opinion, was a design presented by Del the Cat some time back, but my quick search could not find that particular thread. Perhaps Del will chime in and provide us a link to his project description...

Here's another design, from Moose:

http://cr4.globalspec.com/blogentry/4969/DIY-Solar-Hot-Water-Panels

and from frankd20:

http://cr4.globalspec.com/blogentry/4237/DIY-Solar-Heater

There are probably more here on the Forum, plus many links to other sources. Search all of CR4 for many suggestions...

Ditto, Del has some nice pictures and diagrams for his roof mounted water heater. For the larger projects, some research is definitely in order to determine requirements and factor in the insolation rates for the installation location.

For instance, in southern climes, the coating on the collectors probably wouldn't have a huge effect but up north where the outside temperature is much lower, a selective coating would probably be more cost effective versus just 'paint it black' approach. And the type of glass can have a significant effect too. Again, it depends on how many BTU's you are trying to squeeze out of old Sol.

There are a good number of commercially built solar collectors but I would spend plenty of time researching the topic before charging off on this endeavor.

Here are some sites for food for thought. I have no affiliation or attraction either emotionally or financially to any of them.

I'll start with the NASA site on insolation. Here you can register and get information on the insolation rates for your specifc location. It's one of the first places to start if you are going to understand how much energy you can reasonably collect.

http://eosweb.larc.nasa.gov/sse/

Here is another solar calculator

http://www.anotherurl.com/therm/sol_calc.htm

This is a good site from the NREL

http://www.nrel.gov/renewable_resources/

A comprehensive report on renewables

http://www.nrel.gov/docs/fy10osti/48178.pdf

The following are some commercial sites in no particular order.

http://www.solarpanelsplus.com/

http://www.dawnsolar.com/

http://sunearthinc.com/

http://www.thermomax.com/

Radiant heating supplies

http://www.pexsupply.com/

Pumps and circulators

http://www.taco-hvac.com/

Cheers !

Here's a couple more interesting sites:

Space heating:

http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12490

Domestic hot water:

http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850

Thanks for the links, lots of info. I read them all, and then some. Still have some questions that might only be answered with some experimentation, but here is one of the variables.

I have two 48" x 74" double pane windows from an 8' sliding glass door. Would double pane be beneficial or detrimental to efficiency?

Not good. Each pane will reduce efficiency and if they are a low-E glass they will be very poor.

It might be worse than low E, but better than nothing. The glass is early 70's and has a greenish tint! (that won't won't help) I will separate them (carefully) and use one layer. I was concerned that top glass would have no support in the center and that it would eventually fog when the sealant failed. Now, I can make twice as many panels!

You can always put a thermometer behind the glass and compare it with a pane of regular glass to see if there is a difference when the sun is shining through it. Tape a thermometer to the backside of a square of black paper and place that about 1/2 inch under the glass. Make sure you use the same amount of exposure time for both tests.

The tinting will likely cut some of the solar energy, but a simple experiment will tell you by how much.

If you are handy with sweating copper tube, you can bend sheet metal on a brake, know a little something about designing for thermal expansion (hole tolerances, gaps), I would go for it. The tricky part will be getting a good thermal interface between the collector sheet and the copper tube.

Even if you don't have the most efficient design, I suspect the money you would save over buying a commercially made unit will more than make up for any losses in efficiency. Never mind you will have the personal satisfaction of "I made it".

You could even build the collector box out of wood if you didn't want to go the route of a metal enclosure. The foil-backed foam insulation boards at the local big box store are inexpensive and just the ticket for insulating the enclosure. The glass and the copper are probably your most expensive components and you already have the glass. Watch out for moisture build up and condensation. A couple of small louvered vents will help keep moisture at bay at a slight loss of efficiency (venting some hot air).

Good luck with your quest. We'd love to see pictures of your finished product when you're done.

Thanks for reminding me. I have some white alum. coil stock. I think I have every thing but the copper tubing and I have the tools and skills to build pretty much anything from a ESXi virtual machine host to a house (mainly I do remodeling, renovation, and repairs for money and build Linux servers for fun.)

What do you think about contoured (roughly a U shape around each pipe) white metal on insulation to reflect on black painted copper tubing under glass to minimize the amount of copper I will have to buy?

Due to financial contraints, I've had to adopt the 'Use it up, wear it out, make it do, or do without' mentality. So I'll have to use the tinted glass.

Take a look at some of the commercial designs. You will note that the copper tubes between the manifolds are spaced about 4 to 6 inches or so apart with just black absorber plate between the tubes. The black plate heats up and transfers the heat to the tube and the liquid medium. Schematically it looks something like this:

I can appreciate the cost aspect. Other issues can arise from dissimilar materials in contact with each other (galvanic corrossion) Unfortunately, I have not had much luck soldering plain aluminum to anything. Others on this site may have some techniques that work. There are aluminum brazing products like Alumiweld (I have used successfully) and others but I don't know how it would work with copper to aluminum interface.

Is the white aluminum coil stock a tubing material or continuous sheet? I'm not familiar with that terminology.

This is the thin prepainted sheet metal 2' x 50' roll. It's for facia and trim. Very white, if it stays clean. I was thinking of instead of an absorber plate to just put as much light as possible on the copper tubing. With the proper radius the sun could be directed from a large surface area onto the copper tube.

Has anyone built a collector that circulates black dyed water or solution under glass? It seems the most direct route.

Sounds like a series of solar concentrators under glass. Certainly feasible but my concern would be that the unit would only be efficient for a very narrow band of time. Solar concentrators have to be aimed at the sun to be effective. A flat plat will absord solar radiation at almost any angle (of course with an effective reduction in aperture, i.e. the sun "sees" a much smaller rectangle of absorber plate when at low angles versus high angle).

The blackened water idea is intriguing. That is one case when you would want the double pane concept so you wouldn't conduct the heat back to the ambient air.

One downside of the black water is that it would require some type of shallow tank sealed to the glass. This could be more expensive and problematic than the copper tubes.