Solar Concentrator PV Systems --> use some optical system to focus Sunlight onto a PV Array. Examples shown below:



The idea is to essentially take a large collecting area and focus it on a smaller area, thus concentrating the incoming sunlight and therefore increasing the incident energy on the PV. This means that less PV material will be required to produce a given amount of energy and this, potentially, saves expenses. However, current projects are not proving to be cost effective: Ideally the LCOE (levelized cost of electricity) should be 5-8 cents per kwh for competitiveness with other sources of electicity generation.

As of end of 2011 in the US there was only 1.9GW of installed CSP (compared to 40 GW of wind).

There are other CSP projects in the world but they too are not yet cost effective.

The issue then becomes the reliability of the CPV components over time. Also CPV systems function best under clear sky, direct-sun conditions. Early installations were made in Saudi Arabia, Arizona and at Alice Springs, Australia.

Costs are a strong function of DNI (Direct Normal Irradiance):

The primary potential problem here for any CSP system is heat load and subsquent failure of either the PV material itself or one of the components in the optical path. Within CPV systems, the concentration rato can have high variance. If light that falls on 100 sq. cm of reflector surface is focussed onto a 1 sq. cm surface of PV material, then the concentration ratio is 100. Current commercial design concentration ratios are in the range 200-300 suns. Concentration ratios of more than 1000 have been produced by start up companies that have claimed to "solve" the energy problem but those companies, like their components, quickly melted.




Various Designs for CSP systems are shown below:

Linear Fresnel Lens:




Advantage = simplest system and light weight. Focus is "horizontal" and not parabolic. Can be made Large or small

Linear Array for Power Tower



In this case a network of mirrors (heliostats) mostly surrounds a central tower. That reflected and focussed sunlight heats up some kind of receiver at the top of the tower. That hot liquid, usually molten salts, then mixes with water to make steam and hence electricity. This process is shown below.



Many urban centers contain large areas of toxic or unproductive land. These are called brownfiels and are usually the result of some factory that use to be located at that site but has long been torn down. Abandoned gas stations are smaller scale examples of brownfield. Some cities (Chicago, Cleveland, Philly) have quite large areas of brownfield. One advantage of a brownfield is that a grid connection is already there (since a factory used to be there). So why not turn this brownfields into electricity production sites using PV arrays?

One successful example of this is shown below for Chicago:


The Urban Brownfield Array (chicago)

Before the installation



Many commercial systems now use something called a parabolic trough: Here the focus point of the parabolic trough is a receiver pipe. The pipe is filled with oil (not crude oil) and is heated to about 400 C. This heat energy is then used to generate electricity in a conventional steam generator. Solar trough farms are now being constructed (at a slow pace) in some locations in the American SW. The Nevada Solar One: plant is a good example of a small scale project



We can use the details of construction of Nevada Solar One as a model to scale from:

  • Output = 64 MW
  • Cost = $266 million = $4.15 per watt (remember wind is 1.5-1.7 $/watt)
  • Project footprint: 400 acres = 40 MW per square km
  • 28 jobs created = 2.2 Jobs per MW
  • Construction time line = 16 months = 4 MW per month

All renewable energy projects need to be evaluate in the units just presented!

Now let imagine scaling this up by a factor of 10 to 640 MW to serve Eugene. What kind of footprint would that have in say a sunny location in Eastern Oregon?



What would be required to do this?

  • 2.7 Billion dollars (high up fron cost)
  • 280 workers


If this facility had a 30 year lifetime, then that 2.7 billion dollar sticker shock is really $90 million dollars a yeaar for 30 years. Oregon already spends about 1 Billion dollars a year on core infrastructure projects so this is a drop in the bucket.

Suppose you wanted to put the project cost entirely on Eugene residents. According to EWEB there are about 75,000 residential customers in Eugene. That translates into $1200 per year per residence to build this facility (from which each residence would get "free" electricity during the day time).