Pros:
PV produces electricity; has lots of consumer awareness; and now has widely available incentives in the US with 'net metering' policy that allows grid tied solution (think storing when producing and not using).
ST produces heat and is highly efficient; energy is easily stored; the carbon payback from production is rapid; and several new technologies address electricity.Cons:
PV comes with a significant manufacturing impact (high energy loads, high carbon release, plus transportation); is very low in efficiency; production is not aligned with peak load demand; and there is no reasonable energy storage option.
ST is not plug and play; has few cost offset incentives; and offsets natural gas which is cheap.
Near Future:
PV is seeing a number of breakthroughs on the efficiency scale but related economics will need to mature. The storage option could be well aligned with the e-vehicle revolution and grid intelligence but that will take a number of years to really flesh itself out to a state of robustness, and comes with a significant cost in infrastructure. We are starting to see utility scale economics work as the manufacturing base over-supplies the market demand. Technology break throughs are needed and much R&D monies are being deployed to both efficiency and storage research.
ST is seeing a nice resurgence with a number of high quality products and new technological approaches that move far beyond heating water. We can now do space cooling in addition to space heating; commercial scale hot water; industrial scale process water and even process steam; and the coolest approach is utility scale CSP (concentrated solar power). Major Incentive programs are just now becoming available, in some states, and gas utilities are pursuing how natural gas can offset peak electricity demand!
Applications:
PV - micro scale consumer devices; residential electricity; commercial electricity; community electricity; and utility scale electric power.
ST - residential hot water and space heat; commercial hot water, space heat, and space cooling; commercial process water; industrial process water and steam; district energy scale space heating and cooling; district energy scale electric generation; utility scale electric generation.
Economics:
The rule of thumb on PV with both federal 30% incentive and utility based incentives are about a 10 year payback to ROI with another 10-15 years of free energy after that. Electricity has a fairly stable price, but it is trending upward and will continue to do so as State's adopt renewable energy portfolio standards.
The rule of thumb on ST looks about the same at 10year payback with only the 30% federal tax credit, but that is entirely dependent on the cost of the legacy fuel. When put against natural gas, although a volatile priced fuel, paybacks are way out at 20yr but when local incentives are applied we're back at the sub 10yr point. When up against propane the economics are awesome, on the scale of energy efficiency payback of 3-5yrs. Add local incentives to that and paybacks can be 1yr. When you can offset electricity we look like a 5 yr payback; and against heating oil near 7.
However, it shouldn't go without addressing that PV is virtually plug and play at scales below 250kW. A recent study shows economies of scale around 100kW that don't appear to exist at larger scales. ST takes piping and even though plumbing is no big deal there are more holes to cut and flows to address. Economies of scale definitely fall away from small in favor of large for this reason, and lean heavily toward commercial and industrial installations. Although, a residential system can simply be a packaged kit which doesn't seek to offset all hot water needs. A simple cookie cutter approach can cut down on soft costs.
Technologies:
For solar thermal we are seeing special glass glazing that pull in more sun yet radiate less back; we are seeing concentration technologies; advances in evacuated tube; hybrid technologes; and now combined systems that use solar drivers as 'when-available' engine with boiler based hot water as the base source.
What to Watch For 2011/2012
Natural gas volatility due to speculation and environmental regulation.
State based policy and incentives.
Commercial and industrial applications.
Space heating and cooling.
Solar thermal utility scale electric.
Thermal electricity from both direct solar and indirect waste heat.
Tune into the Solar Thermal Alliance of Colorado [COSEIA] for legislative activity.
http://www.cleanenergyauthority.com/solar-energy-news/solar-thermal-alliance-of-colorado-111710/
