zawy

Solar Power Will Be Transformational in the Next Decade

Jack, you changed the input data to "prove" your point. We were talking about 13 cents/kWh and you're using a gracious "effective-efficiency-... of 30 years instead of the standard 25 years. A 3rd source of fudging is that you didn't do APR correctly. Even with your gracious 30-year effective-efficiency-l... monthly payments would be $60, so the rate is 16.4 cents/kwh instead of 15.

If you'll look at my comments, you'll see that i similarly found that $5.4/W is break even for 7% loan and if electricity costs rise 3% a year and if we can get a interest deduction, so we're not really in disagreement. I just want the math and assumptions to be correct and precise. Being off just 1 cent/kWh over 30 years is $3,900 on a 6 kW system (about $2000 in today's dollars when adjusted for inflation).

Solar Power Will Be Transformational in the Next Decade

Your article doesn't take into account the upfront costs when calculating payback. You assume banks will give out 0% loans on the initial $30K investment, or that rich people who can afford the upfront costs are satisfied with 0% return on the investment. If electrical grid energy costs increase 3% per year and you or your bank are satisfied with 7% return on the $30K investment, you have to use a 7%-3%=4% depreciation factor. In this scenario, the $4.5/Wp installed costs you propose in a typical 6 kWh/day/m^2 location (this includes clouds!) at today's 13 cents/kWh, it will barely break even over the 25 year "efficiency-effective" lifespan of the solar cells. If it's in a new house where you can depreciate the home interest expense and are in a tax bracket of 25%, then the depreciation factor is 7*0.75-3=2.6% then payback can occur at $5.4/W installed which i believe is very doable.

There is no simple energy storage solution. The raw materials in EEStor supercapacitors cost $10/kWh, about 50 times less than current generation lithium-ion. See BCON for 10-hour energy storage with 25-year lifespan that could cost less than $1/kWh. Even at $1/kWh, storing half the energy of Jacks $30K, 7kW system in 6kWh locations will cost 7x6/2= $21K. Flywheels with carbon nanotube technology ($4/pound in 5 years) could solve the energy storage problem. They use vacuum and magnetic floating to keep 80% of the energy for 12 hours. Currently used in energy storage for cranes, trains (start/stop regeneration), and telephone systems.