Part 2: Solar and Wind Solutions to a Zero Carbon Grid

R. McCarter

A Solar Grid

Solar is often sold as cheaper than other electrical generation with capital costs per installed kilowatt of $1313.00 and no additional fuel costs. The capital cost of natural gas is somewhat cheaper at about $1020.00 per installed kW but then there is that large fuel cost. Nuclear power has a high $6041.00 per installed kW and has fuel costs as well. But there is more to electricity production than capex (capital expenditure) and fuel.

Over this recent fall and winter period, I calculated the German grid’s solar capacity factor had a high of 17.6% and a low of 0.48%, rounded, that is the solar installations produced between 0.5% and 18% of the total rated capacity you paid for. For this half year, the average capacity factor of the solar plants was 5.71% with a low average of 1.7% over the 30 day period around the winter solstice. Fraunhofer calculates solar to have had a 10.5% share of the grid in 2020, which I estimate as a 9.9% solar capacity factor over the year, however, grids don’t work on averages, they have to supply enough power to keep the refrigerators cooling and the furnaces heating, even at the least productive times.

With a minimum of 0.5% capacity factor, and with those pesky non-productive nights, there is no full solar solution without excess capacity and storage. With a full winter month of very low capacity factors, the excess capacity has to be large and pumped hydro or battery storage has to be huge. This graph details a possible solution that is generation heavy and storage light. The orange line as before is the load, the power needed to keep the grid working.

5600 GW Solar, 140 GWd Battery

The blue line is the power generated from an installed capacity of 5600 GW of solar, over 100X the present installed solar and would cover 112,000 km^2 or about 31.3% of Germany. This would produce a lot of excess energy for much of the year and this would be used to charge a 140 GWd (GigaWatt day) battery, enough energy to supply the grid for a little over two days.

The battery charging and discharging is shown by the red line, flat-topping at a fully charged 140 GWd (gigaWatt.days) and bottoming out at zero when fully discharged. 

Over this past half year, neglecting inefficiencies of charging and discharging batteries, the system would have continued to supply enough energy to keep the grid running with only one day, January 8, 2021, with the grid near failure. Even a small reduction in this solar capacity or battery storage would result in unacceptable grid failure for several bitterly cold days.

Using approximate costs from the US EIA (2020), the solar installation would cost $15,180 billion USD and the battery would cost $1166 billion. Cost of the electricity produced would be about $0.135 without costing for the battery, however, a lot of the spring, summer and fall generation would have to be shed or sold to neighbouring countries. Present excesses of the German grid are produced at odd times that do not match needs of the neighbouring countries  and are sold at low or even negative pricing.

Over a 40 year period, using a solar installation life expectancy of 25 years and battery life span an expected 10 years, the wholesale costs, without profit, would be $1.089/kWh. If I then use a generous 40% discount in battery installation for the latter 30 years, I estimate the economic cost of this project to be $20,179 billion, the environmental cost as catastrophic, and the cost of electricity a lower but still an economy destroying $1.015/kWh. In BC, Canada this would increase electricity bills by 9X. Instead of paying $350 a month, I would be paying $3000 for the same amount of electricity.

The GDP of Germany for 2020 was $3800 billion and this system would cost $504 billion a year over 40 years, fully 13.2% of the economy to get the same amount of electricity Germans have now.

There has to be a better solar solution with lower generation and large storage.

1750 GW Solar, 2000 GWd Battery

The above solution uses 1750 GW of installed solar capacity on only 35000 km^2 or 9.8 % of Germany. At this capacity there are about 70 days with a shortfall of energy and therefore the need for a very large battery. I calculate the needed battery at 2000 GWd, enough energy for about 32 days. The estimated cost of this solar capacity is $2298 billion and the battery cost would be $16,656 billion.

In 2020, batteries were installed at $347.00/kWh. Several articles I have read trumpet that this is far cheaper than the $1020/kW for natural gas or the $6041/kW for nuclear, but these authors confuse energy (kWh) with power (kW). Batteries do not produce electricity they store electricity generated from another source. The cost of batteries has to be added on to the system cost, an extra cost of intermittent electrical production that is often not accounted for when marketing wind and solar.

Over a 40 year period, with a solar lifespan of 25 years and battery lifespan with the expected 10 years, the levelized wholesale cost for electricity would be $4.84/kWh. Discounting future battery installation by 40%, the total cost of this system would be $76,149 billion, 50.0% of the Germany economy over 40 years. The estimated cost for each kiloWatt.hour generated is $2.175 including surplus electricity. If the only revenue is from electricity used by the grid, this would be $3.83/kWh That is 35X what I am paying now, a monthly electrical bill of $12,000.

“But what if battery costs drop by half?”  

Nope! the above calculations drop battery prices by 70% for the latter 30 years of life span. 

“What if solar panels increase in efficiency?, panels cost less to produce?, or the panels are moved to Spain?” (Where they are only too happy to cover their landscapes to help Germany.)

The solar panel modules represent about 36.5% of the capital costs, so a cost decrease by 50% will only decrease installation costs by about !8%. Moving to a compliant Spain can increase solar insolation by about 50% though transmission costs and losses increase. It is possible that solar cells may increase from a present 20% efficiency to 30% efficiency. The highest laboratory efficiencies with multilayered solar cells reach 40%. With increased insolation and efficiency, future Spanish solar electricity could be a 100% improvement reducing land covered to 17,500 km^2, 3.5% of Spain, and reducing electricity to a much more reasonable $6,000 a month to get what I am getting now for $350.

I can think of no better way to destroy your economy, devastate your (or someone else’s) environment and impoverish your people than to dismantle your current electrical grid and replace it with an all solar one. Surely that is not part of the plan?

A Wind Grid

Like solar, wind is a a diffuse intermittent energy source that needs a lot of land and rapid response backup generators or battery storage. As wind power rapidly rises or falls, backup systems have to ramp up and down to follow the load. In a hypothetical ‘zero carbon’ world, gas turbines are out and hydropower is limited so we are likely to be back to batteries.

The existing 62.59 GW of German wind power have a 24.0% capacity factor over the given fall/winter half year from September to March. To produce enough energy to satisfy the load over this period would require an installed capacity of 240 GW, however, there is such a lull in the wind through September there is not a reasonable solution for the battery storage to prevent collapse of the grid.

There is a solution with 370 GW of installed wind capacity and a 190 GWd battery, enough storage for 3 days. Again the orange wavy line is the load, the power that must be supplied to keep the grid running. The blue peaked line is the generated wind power and the red line is the battery storage. 

370 GW Wind, 190 GWd Battery

According to my spreadsheet this system would cover 120,250 km^2, which is 33.7% of Germany.  A bargain compared to solar, the wind turbines could be installed onshore for $468 billion with a possibility of offshore installation for $1619 billion, almost 4X as much. The battery installation would be $1139 billion at a present-day $347.00/kWh. With lifespan a generous 25 years for turbines and 10 years for batteries, including a 40% future drop in battery costs, a 40 year cost would be $7922 billion or 5.2% of the German economy over the four decades.

If all of the generated electricity is used the cost could be as low as $0.254/kWh, a wholesale price.  But with unpredictable fluctuations occurring at inconvenient times, the excess generation would have to be either shed or exported, likely at negative pricing. These losses could increase the cost of wind generated electricity to $0.392/kWh. So only 3.5X what I’m paying now, only $1225 a month, though I’m comparing a levelized wholesale price to my retail price.

There have been suggestions to store excess electrical energy as hydrogen gas that could then be used to provide heat or transform back to electricity. The efficiency for electrolytic hydrogen production is 70-80%, then a 60% efficiency for fuel cells to produce DC electricity, another 80% efficiency for DC to AC. That is about a 36% round-trip efficiency for hydrogen energy storage compared to an 80% efficiency for most batteries and a 90% efficiency for newer Li cells. 

Hydrogen is a problematic fuel, requiring high pressures to get energy densities needed for transport. It is highly explosive in a wide range of concentrations, and embrittles metal containers and pipes. One solution is to chemically combine the hydrogen with captured carbon and use these carbon/hydrogen compounds to store hydrogen relatively safely at low pressures. Heating releases the hydrogen to burn in air, providing heating or the energy for transport. Amazingly, these fuels can be used in existing furnaces or engines. The energy efficiency of conversion of hydrogen to methane is estimated at 41% making these fuels expensive compared to my usual sources of hydrocarbons. 

Solar and Wind

Solar can be more reliable than wind and can supplement on windless days. There should be a less costly grid solution that uses both wind and solar.

Here is one solution that would have kept the grid from failing for the past half year:

380 GW Solar, 420 GW Wind, 90 GWd Battery

With 380 GW of solar and 420 GW of wind, there is a lot of excess electricity to be shed, exported or inefficiently stored as hydrogen. The system occupies 144,100 km^2 of land, 40.3% of Germany. But hey! Who would’t want the nearby fields covered with solar panels or a 100 m high wind turbine to look at all day. The battery holds only 90 GWd or storage for about 1.5 days. The capital cost of the solar is $499 billion and the capex for onshore wind is $531 billion. The installed cost of the battery is $750 billion.

A 40 year estimated cost with a generous 25 year life for both solar and wind and a 10 year life for batteries and a 40% decrease in future battery costs is $5536 billion or 3.6% of German GDP. For all of the electricity generated that is a wholesale price of $0.13/kWh, however, if the excess electricity is not profitable, the wholesale lowest cost of the grid electricity would be $0.275/kWh. Note that retail costs will be higher.

This is a minimal system, it is recommended that these intermittent grids have at least 25% backup. Although the above system should work over the past half year used in these calculations, there is no guarantee for future years that may have longer windless periods during the coldest days of the year. The dispersed exposed collectors for wind and solar can be vulnerable to storms, the worst weather days when electricity is needed the most.

Do you want to impose this on future generations, your children and grandchildren?

The above costs are estimates based on 2020 prices and will change with time. Solar panel costs and batteries have been falling, but don’t be misled. There are improvements in solar panel manufacturing and efficiencies but the panels themselves represent only about 37% of the installation. Even a large 50% decrease in solar module cost will therefore only decrease installed costs by about 19%. 

There are estimates that batteries will soon be under $100/kWh. That is a battery only cost and there are many more expenses to setting up the grid scale battery, including inverters, transformers, cables, construction, land … Of the 2020 battery installation cost of $347.00/kWh the batteries are $200/kWh or 57.5% of the capital cost.  Halving of the battery cost would reduce overall installation costs by 29% to $247/kWh.

Not taken into account in my estimates are the losses in performance of battery systems over the years and at different temperatures. Also not included are the recommendations to lower the charging to 90% of capacity or less to increase the number of duty cycles. Taking these factors into account makes the costs of wind and solar even more problematic.

In Part 3 I will take a look at another zero carbon solution and compare its costs to those of wind and solar. I will also summarize the possibilities of zero carbon solutions.

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