The beginning of the future - Heat focusing solar power plant approved

If my arithmetic is correct, this works out to be about 10 square meters a person.

 

This is the typical American way, now applied to solar--do it big and inefficiently. If instead every roof in the US had a few solar panels, we would eliminate the need to do a massive upgrade to the electric grid, and avoid the line losses that make central power plants so inefficient. Most large plants are ~25% efficient, and I'd bet this large scale solar will be similarly poor.

 

Line losses aren't a big issue and large plants of the same technology and age are typically more efficient than smaller plants.

 

... and home PV is about 13% efficient.

 

When they are clean and new

 

When you consider how many square meters of solar energy are needed to feed a cow (via photosynthesis), 10 sq. meters does not look so bad.

 

Especially when you use roof-tops.

A small, reasonable percentage of desert land makes sense for solar energy too.

 

Sorry, but that is a worthless number. 13% compared to what? A brick? Or a shingle?

When one talks about PV efficiency, there are two numbers to consider, the first, which is indeed correct. You are correct in that number, as PV modules convert about 13% of available sun energy into electrical energy. In the real world, it doesn't really matter(within reasonable size/dollar constraints) if a PV converts at 1% or 50%, as long as the price per watt hour is as low as possible. A panel that converts at a higher efficiency, but a higher still cost is no bargain.

The second, and much more important efficiency number is how efficiently any energy source gets to the end user. A typical grid tie PV system will convert in the 75%+ range out of an AC inverter. (Standard derating numbers, in actual fact, a PV in full sun will convert upwards of 90%) A typical battery based, off grid system will convert at about a 50% rate.

So the issue here is not the basic efficiency of the PV, or even so much the conversion efficiency, but how that power gets to the end user. Obviously, the user closer to the generator is fundamentally more efficient, and likely cheaper. The counter point to that is that large scale PV, properly sited is likely to be very much more productive than random average of roof top PV. Additionally, the economies of scale are such that large scale PV is likely to be significantly cheaper on a KWH basis.

My good example of this is the difference between rainy, grey western WA, vs Sunny Eastern WA. Right out of the gate, an installation in Yakima gets a 25% advantage over a similar sized installation in Seattle just due to weather conditions.

So in the words of real estate speculators everywhere, location, location, location! Site location, distribution location, and end user location!~

 

Neither brick or shingle, just somewhat average TD efficiency of PV modules being sold for home installation.

I agree with you that this number is not adequate information by itself to judge the economic merits of roof vs central power, but base central solar power TD efficiency is I think easily twice rooftop. That is quite a difference to make up.

I gather the economics of centralized solar are greatly affected by cost to bring the energy to the consumer. If the infrastructure is present central solar wins handily, but if the lines have to built the cheaper route is a ymmv.

 

Sage<

I'm sorry but there two things here I don't understand. What is "TD" efficiency? Second, what is "ymmv"?

As a result, I don't understand this

 

ymmv is "your mileage may (will) vary
TD is thermodynamic

 

got it.

Question is, is it thermal dymamic ef that we really care about, or ultimate capture/conversion of energy? Doing it at higher TD ef may have a benefit, but as I said earlier, is it cost effective. Except for space issues Pv conversion efficiency is largely irrelevant. Producing PV at 1/2 the cost per wh is much better, IMHO, than producing it twice as "efficiently", but at the net, out the invert wh cost.

Simple solar hot water systems capture at a much higher percentage, which is why first out of the box for a solar installation should be hot water, (unless you use hot water recapture heat pump technology.).

 

The total cost of a PV installation includes the structure to protect and support the PV cells, installation costs and some more details. The total cost for the non-PV cell hardware of the on the roof portion of a PV system can easily cost 1/3 of the total cost of the stuff on the roof.

As efficiency goes down, area needs to go up for the same total power and nearly all associated on the roof costs are directly proportional to the total on the roof area.

I have also noticed that some of the home PV installations in my community cover nearly the entire suitably oriented roof area. With lower efficiency cells, they would have had to make do with lower power systems.

I would agree your argument is valid if you are comparing reasonably high efficincy mainstream PV cells with bleeding edge technology PV cell$

 

XS,

I am not suggesting that efficiency gains in PV conversions is a good thing, but on balance, given the choice between a $10/watt 25% eff panel and a $2/watt 13% panel, there is no contest,, unless you absolutely have no space for the larger, less efficient PV.

Icarus

 

Solar thermal requires very precise controls to focus that heat. Doubt the technology was there anytime before the transistor to get it right.

As to the comments about "big"... CSP works best at the utility scale. Residential CSP is out of the question... doesn't make any sense there. PV is a much better solution at that scale.

At the utility scale, CSP makes much more sense than PV. It's cheaper, takes up less space (given the current SOA of PV) and is much more cheaply stored for later use via molten salts which are, incidentally, more efficient than batteries.

Each technology has it's place. PV is great for residential and commercial scale power production (preferably on rooftops as was already mentioned). CSP is an excellent option for utility scale production. It has the added advantage that you can hook up NG and have a production factor close to 100, which makes such a plant pretty attractive to investors which is important at these large scales.

 

Fossil fuels had the advantage of having a very, very good return on energy investment. For a very small amount of work, you can get a LOT of fuel out of the ground. In some places, all you had to do was put the bucket in the right spot.

Now that all the easy oil is gone in sufficient quantities, lower EROI options are becoming viable.

 

Because of the inconstancy of Solar power and the expense of energy storage. These problems remain today.

 

You forgot the obvious answer that solar power stored as heat can also be tapped at a later time, in some cases 24-48 hours later in the case of using molten salt. This reduces considerably the problems with PV panels, which are useless at least 12 hours a day unless you invest in an expensive battery pack.

I'm not doubting you, but where'd you get that number? I didn't see anything in the article that gave the size of the installation, or even what type of solar thermal technology they're using.

And parking lots. Most people given the choice would prefer to park in the shade.