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Armstrong: The cost of Virginia solar

Armstrong: The cost of Virginia solar

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By Jim Armstrong

Armstrong is a Professor Emeritus of Electrical and Computer Engineering at Virginia Tech. He lives in Blacksburg.

The General Assembly recently passed legislation making zero carbon power a goal to be reached by 2050. Let’s see how Virginia might try to reach it’s goal. Significant wind power offshore is 10 years away but solar could be deployed in a few years. So we should concentrate on it now. The average generated power for Virginia is about 20,000 megawatts. Suppose you wanted to replace half of this by solar. Since average solar power is 1/6 of rated power in Virginia, 60,0000 megawatts of solar would have to be installed. This generation incurs land and dollar costs. Data from existing large solar projects in India and China shows that at least 6 acres of land per megawatt is required. Thus, 60,000 megawatts would require 360,000 acres. At a cost of $500,000 per acre, the total solar panel cost would be 180 billion dollars. Our plan is much bigger than any existing project such as the 2,245 megawatt Indian Bhada Solar Park! But to accomplish our goal, we need it.

Montgomery County has an area of 249,000 acres. Suppose you put most of the solar farm in Montgomery County. The real estate of value of county land is $8 billion. Retiring this land would be a significant blow to the local economy. Also the total household income of Montgomery County is about $2.23 billion. 100,000 people reside in the county and would be displaced. Maybe you don’t want to put the solar farm in one county (whew!). But even if you distribute it, the same sort of land loss, GDP loss, and displaced population would occur somewhere in Virginia

Because sun power is intermittent, you would need to store power. Suppose you wanted to store the solar average power (10,000 megawatts) for 6 hours, i.e. 60 billion watt hours. Currently lithium ion batteries are the choice for storage. But the term battery here actually means a storage system consisting of a battery, battery management system, and a power inverter. Tesla used such a system called Powerwall in an Australian wind power storage project. The project stored 129 megawatt hours and cost 95 million dollars, .i.e. $.736/watt hour. Using the same technology, our storage would cost 44 billion dollars

So, let us summarize. For $224 billion and a land penalty of 360,000 acres, 100,000 people displaced, and a $10 billion hit to the local economy we could potentially reach our goal. But let’s evaluate our proposed system.

The big problem is the battery. The life of the lithium ion battery is 2 to 3 years.

So you be replacing a significant number of batteries every year. Also very large arrays of batteries would be required. Tesla now makes a Megapack which has 3 megawatt hours of storage. For our storage system, 20,000 Megapacks would be required. How do you monitor them all reliably? Total world production of li-ion batteries is 160 billion watt hours. We would use 37.5% of this production. What about the rest of the world’s storage needs?

Finally our storage strategy is suspect. On a normal day, with normal sun, a solar panel produces a trapezoidal pulse of power during the morning and afternoon. If this does occur, our strategy of storing 6 hours could work. But what happens if it rains all day. You have nothing for the evening. A home owner with home solar might not care. Just buy some power from the grid. We are the grid. Maybe we need to store two days of power. Way too expensive. Thus, all existing energy storage systems and those planned, are back up systems which provide extra power during peak power periods only. They don’t provide steady power support. Thus natural gas back up is still required.

So where are we at? A $224 billion price for big solar is a price that might be afforded if we had a system that gave us continuous power and would last for 10 years. We don’t know how to build that. But the solar panel system we propose would significantly reduce our carbon footprint. So maybe we should do it any way. Should we gamble? That’s the question.

Maybe you don’t like my plan for renewables. Then let’s see yours. Be specific. No hand waving. Come with numbers.

Finally, note that the Mountain Valley Pipeline cuts through your meadow. Solar panels cover up the whole meadow. Pick one?

Edited July 2, 2020 to correct dropped word.

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