Posted on 04/01/2016 8:04:15 PM PDT by Ernest_at_the_Beach
Guest Blogger / 6 hours ago April 1, 2016
Guest essay by Philip Dowd
Here is a simple example that illustrates why current solar technology will be hard-pressed to replace existing carbon-fired power plants.
Let’s suppose that a power company is planning to scrap a coal-fired power plant and wants to replace it with a new plant. Furthermore, let’s assume that the old plant to be scrapped is in Arizona. The options for the new plant are natural gas and solar. The company wants a simple, ball-park analysis of the front-end cost to build each of these options.
The requirements:
1. Electricity demand on this facility is 4,800 MWh/day, about the demand for a community of 160,000 average households[i]
2. The “up time” of both plants must be equal. That is, both must be equally reliable and produce the demand for the same fraction of time over the course of one year.
Assumptions:
1. The solar plant will consist of a Photovoltaic (PV) panel and a battery. The PV panel will generate enough electricity during the day to produce the necessary output and charge the battery. The battery will generate the necessary output at night.
2. Night time demand equals day time demand.
3. The new plant will be built in Arizona, a good spot for a solar plant
The Analysis
The analysis is in the form of an annotated spread sheet, showing the two options and the steps required to derive the solution.
I. Capital Cost to Generate Electricity
II. Capital Cost of Storage for Night Time Demand
The solar option requires a battery that would supply night time demand. For this purpose we will use technology known as “Pumped Storage”. This method stores energy in the form of potential energy of water, pumped from a lower elevation reservoir to a higher elevation reservoir. In our example, about half of the electric power from our solar facility produced during the day would be used to run the pumps and fill the upper reservoir. Then, at night, the stored water would be released through turbines to produce the electricity that would run the night time economy.
For more on this see: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
III. Total Capital Cost Including Storage ($millions)
For our exercise let’s consider the Bath County facility, located in the northern corner of Bath County, Virginia[vii]. It was constructed in 1977-85 and is currently the largest pumped storage facility in the world.
Here are its relevant specifications:
So, at this point in the exercise we have the relative costs of the two options to generate electricity over a twenty-four hour period, assuming normal operations for both. The capital cost of the solar option is about 14 times the cost of the gas option.
Conclusion
This back-of-the-envelope analysis suggests that a solar (PV) power plant that could deliver that same results as a gas-fired power plant would cost about 14 times the gas-fired option to build. It is worth noting that the solar option cost excludes any subsidies, investment tax credits, etc, that could narrow the range, but it is obvious from this little exercise that until solar technology improves dramatically, there is little chance that it will replace natural gas as the “go-to” option for new power plants.
Bill Gates, the co-founder of Microsoft, has said that it was “fantastic” that the UN, national governments, and environmental campaigners had raised awareness of climate change and were taking steps to counter it. However, he argued that current technologies could only reduce global CO2 emissions at a “beyond astronomical” cost. “The only way you can get to the very positive scenario is by great innovation,” he said. “Innovation really does bend the curve.”[xiv]
I totally agree. Mr Gates intends to invest $2 billion in renewable energy over the next five years — innovation to bend the curve. Solar energy is going to need lots of it if it is ever to become a viable substitute for carbon-based energy.
References:
[i] Average household in US consumes about 900 kWh/month or about 30 kWh/day
http://insideenergy.org/2014/05/22/using-energy-how-much-electricity-do-you-use-each-month/
[ii] Net Capacity = electricity demand for one day ÷ 24 hrs or x/24
[iii] http://www.eia.gov/forecasts/aeo/electricity_generation.cfm
Scroll down to the table. Capacity factor is found in col 2.
The number for gas is “Conventional Combined Cycle”
The number for solar is ”Solar PV”
[iv] Gross Capacity required = net capacity ÷ capacity factor
[v] http://www.eia.gov/forecasts/aeo/assumptions/pdf/electricity.pdf#page=4
The cost used comes from col 5 in this chart: “Base Overnight Cost in 2014”
The entry for gas is “Conventional Gas/Oil Combined Cycle”
The entry for solar is “Solar PV”. Note that this cost excludes any subsidies.
[vi] Gross Capacity Required x Capital Cost
[vii] http://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station
[viii] The equation here is Capital Cost at time of construction x adjustment for inflation
For Bath = $1,600 mil x 2.6 = $4.1 trillion (inflation adjustment is for the period 1981 – 2014)
For inflation adjustment use this site: http://www.usinflationcalculator.com/
[ix] The equation here is Capacity x Time to Empty Upper Reservoir
For Bath = 3,000 MW x 14.3 hours = 43.0 GWh
[x] Assume night time demand = day time demand so night time demand on the solar battery = ½ total daily demand
[xi] Cost of Storage = Capital Cost ÷ Stored Energy = $4.1 trillion ÷ 43 GWh ≈ $100/kWh
[xii] Capex to store night time demand = $100/kWh x 0.5X kWh = $50X
[xiii] Total here is the “Total Capital Cost” in Sec I plus the “Cost of Storage” in Sec II
[xiv] http://www.ft.com/intl/cms/s/2/4f66ff5c-1a47-11e5-a130-2e7db721f996.html#axzz3kyDZjQxG
April 1, 2016 in Energy, natural gas, solar power.
Using 4% interest rates (typical corporate bond), solar cost is $0.057 (5.7 cents) per kilowatt hour more than the natty plant.
It’s a ridiculous comparison. The solar plant has a huge footprint, no one is allowing new pumped storage to be built, no one wants power lines in rural areas where solar must be sited.
Natural gas costs (real cheap now), solar is free, but solar collectors need cleaning by the acre, must stand up to storms, and will be down during extended cloudy periods.
Electricity must be reliable. Green energy is not reliable and is of limited value as an electricity source.
Dated an Ivy league MBA woman who adamantly insisted that the reason we weren’t exclusively using solar power was because of big business republicans and we weren’t trying hard enough.
The relationship did not last long because she could not tell a watt from a tw@t.
Don’t forget, many PV fields generate tremendously dirty power, when inverting the DC power to AC. It’s much easier to generate clean High Voltage from rotating generators.
Additionally, the more distributed we become on generation facilities, the more complex the overcurrent protection and coordination becomes. We’ll see more power outages from difficult to analyze faults over the next 10 years from all the larger DC applications being added to the grid.
A pumped storage unit is being built in Montana
“http://www.gordonbuttepumpedstorage.com/";
The cynic in me expects someone to stock it with fish and have it shut down. Other than that scenario, it will be interesting to follow.
Seriously? You think the panels pictured pose a threat to birds?
And get rid of ISIS.
I think the perfect solution to our electrical generation problem is to have the prisoners in all jails, prisons and those in welfare lines crank WW-II “Gibson Girl” generators all day long to power the grid.
That will give them something constructive to do and we will benefit from their punishments. What a deal!
I’m just interested - do you know the O&M for each? The feedstock for the gas? The land size for the solar?
Hey, what’s a few fried birds if you are making the correct political statement?
Indeed.
I am seeing a Hillary Fan ....
I know the feeling.
Keep us posted!
They have already documented such.. As the birds fly over the solar farm they get burnt to a crisp!!!
Molten metal battery:
Operative word “MAY”
Not from the type here. These are passive solar panels. You are thinking of the mirror type fields that direct beams to a tower.
here is something from the California Mojave Desert Solar farm..
https://weather.com/science/news/solar-plants-birds-20140818
Yes. Exactly what I told you. Using mirrors to reflect the sun to towers. That will fry birds.
Not the passive panels we were discussing in this thread.
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