An Analysis of Californias Million Solar Roof Initiative

1
An Analysis of Californias Million Solar Roof
Initiative

• Dennis Silverman
• Department of Physics and Astronomy
• U. C. Irvine

2
Conclusions

• We will show here a basic cost analysis of the
  million solar roof plan.
• We will find that the total installation cost
  will be 20 billion.
• The total output from those roofs on average will
  be about half of that of a single nuclear
  reactor.
• Compared to a 1-2 billion cost of a nuclear
  reactor, California could build 10 nuclear
  reactors, for the same money.
• The new nuclear reactors would boost nuclear from
  13 of Californias power to 35 on peak power
  days.
• Along with 19 of hydro power, and 20 of solar
  and wind power, California could have 74
  pollution free and CO2 free power from the same
  amount of money that will be flagrantly wasted on
  the million solar roof plan.

3
Cost of Building the Million Solar Roofs

• The typical photovoltaic solar roof being
  considered is 3 kilowatts (kW).
• The cost of such an installation with an inverter
  to the electric grid is 20,000 for panels and
  26,000 for integrated roof panels.
• Multiplying the 20,000 by a million gives the
  total cost to 20 billion.

4
How much power is generated?

• The 3kW installation times a million solar roofs
  is 3,000 megawatts.
• But wait, that is peak power when pointed
  directly at the sun.
• A rooftop installation does not track the sun and
  is not at the optimal angle for noontime power
  other than one day a year.
• Other problems roof slope not at latitude
  angle, nighttime, seasons, clouds, and the marine
  layer (June Gloom).
• The average power is only 1/5 the installed and
  paid for peak power.
• Therefore the average power generated by the
  million solar roof installations will be 600
  megawatts.
• That is about half of that of the 1,100 megawatts
  of a nuclear reactor.
• It is also only 1.2 of Californias maximum
  power usage of 51,000 megawatts.

5
Comparison to other energy systems

• In Victoria Australia, they are installing a
  solar photovoltaic system with sun tracking
  multiple mirrors on a few, more efficient solar
  cells (solar concentrator).
• The cost of this per kW is half that of the
  cheapest home rooftop systems.
• Even cheaper, large solar concentrator (mirror)
  systems that heat mineral oil or sodium come
  close to the cost of commercial electricity.
• Faced with a choice, PGE chose the solar
  concentrator system to be 1/3 to ¼ the cost of
  solar photovoltaic.
• Since most homes will be connected to the
  electric grid, and draw most of their power from
  it, what is the point of building your own more
  expensive system?
• Also, grid electricity will be 2/3 greenhouse gas
  free in California by 2030 if goals are achieved.
• Bragging rights? Feel good? The rugged hunter
  gatherer? The provider of fire? The survivalist
  instinct? Getting a free subsidy from the
  abstract government?

6
But you forgot about the rebates!

• I have never yet heard from solar vendors,
  environmental groups or self-satisfied home or
  business installers any concern for who pays for
  the rebates.
• It is taxpayers, and to some extent utility
  users.
• In this analysis we will analyze the total costs
  to all involved.

7
Cost of the embedded roof panels and rebates.

• For the 3kW installation the cost is 26,000.
• The million solar roof rebate is 8,400.
• The federal tax rebate is capped at 2,000.
• So the cost to the buyer is 15,600.
• Not only will the buyer be getting mostly free
  electricity, but the installation will add to the
  value of his/her home.
• Thanks for the 10,400 gift.
• The million solar roof bill is only for about 3
  billion, so later installations will get less
  state rebate.

8
Nobody was buying?

• The original bill required the user to pay for
  electricity based on the rate for the hour of
  use. This was costly.
• The new amendment has them pay only the standard
  overall rate.
• However, the original pricing scheme was put in
  to show some economic sanity and competitiveness.
• Solar cells generate electricity during the day
  when there is less demand, and give a lot of it
  to the grid.
• Then at evening when demand is highest (and so is
  cost) the user takes the bulk of power from the
  grid, now without paying extra.

9
But after installation the power is free!

• First of all, the solar panels have to be kept
  clean. In many locations this would mean a
  weakly washing involving lots of water from hoses
  onto rooftops, and the labor of a million
  homeowners.
• Maintenance of a million home electric
  installations has to cost more than in a
  centralized plant.
• The economic analysis by vendors shows a profit
  to homeowners, based on the historical 6.7
  increase per year in the cost of electricity.
• In writing off the energy and pollution cost of
  creating the silicon solar cells, estimates vary
  from 1-2 years of the systems power, to that of
  generating ½ the greenhouse gases of natural gas
  on a lifetime basis.

10
Costs to other Utility users

• Part of the rebates are being funded by extra
  utility charges.
• While homeowners installing solar cells may only
  need 25 of their power from the utility, they
  will only pay 25 of their previous bill, since
  most costs are proportional to usage.
• However, a large part of the bill for most users
  is the cost of delivery, not the power. That
  means the costs to construct, upkeep, and run the
  grid and the link to the homeowner.
• Why should the cost of the grid be cheaper to the
  solar cell home? In fact, they use the grid both
  ways, in sending power to the utility during the
  day, and drawing as much power as anybody during
  the night.

11
But what about passive solar adaptation?

• Usually one would keep a house cool by providing
  shade.
• With solar cells on the most solar exposed part
  of the roof, the house would heat up if they were
  embedded in the roof.
• The house would also heat more if the embedded
  tiles are non-reflecting, and used to replace
  more reflective roof tiles.
• Solar panels might take the place of cheaper and
  more useful solar water heating, which cannot
  take place far from the home.

12
How much free power do I get?

• A 3kW peak system with the 1/5 average power
  generates 3/5 kW 600 W average power.
• Multiplying by the approximately 9,000 hours in a
  year, this is 5,400 kWh (kilowatt hour) per year
  of energy.
• The average household use is 84,500 million kWh /
  11.5 million households, or 7,350 kWh per year.
• So a PV solar system on an average household
  would account for 5400/7350 73 of the power.

13
How long until payback?

• The 7,350 kWh per year at 13/kWh will normally
  cost about 956 per year (this is 80/month).
• If 73 of that is rooftop generated, it will save
  the homeowner 956 x 0.73 700 per year.
• If the installation is the cheaper 20,000
  panels, payback to society will be in 29 years.
• For the more expensive embedded panels at
  26,000, payback to society will be in 37 years.
• Using the price to the above homeowner with the
  rebate of 15,600, the payback to him/her will be
  in 22 years.
• From radiation damage to the panels, thirty years
  is about their lifetime.

14
Monetary alternatives?

• I apologize that I am not an economist to do the
  interest rate calculations to evaluate this long
  term.
• A US government analysis only showed the payback
  for California to be in the 2050 year range.
• However, most installers want to be paid on
  completion of the job, not over 20-30 years.
• The 26,000 in the bank at a 4.5 interest rate
  would yield 1170, more than enough to pay the
  956 yearly electrical bill.

15
Cost Effective Alternative Solar Power

• PGE in Northern California decided on a large
  scale solar thermal facility heating a liquid
  which then vaporizes water and runs a turbine.
  The cost of that system is to be 1/3 to ¼ the
  cost of solar photovoltaic for the same power.
• While the grid can distribute solar generated
  electricity, there is no way to distribute hot
  water to households.
• Here, solar hot water heating at a much cheaper
  cost of 3,000 - 5,000 per household can
  eliminate 50 to 80 of your water heating
  energy.
• Household water heating takes comparable energy
  to the household electricity usage.

16
Conclusions

• We have shown here a basic cost analysis of the
  million solar roof plan.
• We found that the total installation cost will be
  20 billion.
• The total output from those roofs on average will
  be about half of that of a single nuclear
  reactor.
• Compared to a 1-2 billion cost of a nuclear
  reactor, California could build 10 nuclear
  reactors, for the same money, generating 11
  gigawatts of power.
• The new nuclear reactors would boost nuclear from
  13 of Californias power to 35 on peak power
  days.
• Along with 19 of hydro power and 20 of utility
  solar and wind power, California could have 74
  pollution free and CO2 free power from the same
  amount of money that will be flagrantly wasted on
  the million solar roof plan.