Photovoltaic power plants on farmland? Much better than energy crops for cars!
Do the math! Photovoltaics beats photosynthesis. Electricity beats combustion. Disruptions in energy technology call for a faster rethink
The text below was originally published in German as a contribution to a political debate taking place in Germany. Since my estimations have caught considerable attention, and given their relevance for other countries, I thought it would be useful to publish it also in English.
Translation by Dr Wolfgang Hager
May 2023. In his proposal for a photovoltaic strategy, German economy and climate minister Robert Habeck proposes that half of the 215 gigawatt peak (GWp) of photovoltaic installations planned by 2030 should be realized with ground-mounted systems and that arable land should also be made available for this purpose. The environment and agriculture ministries, which are both led by the Greens, are now voicing their opposition. Habeck argues that small-scale PV systems on buildings and residential areas make sense, but are more expensive and slower to implement, and that it is important to move forward quickly. His strategy proposes specific rules for the annual addition of 11 GWp of ground-mounted systems. However, the other two ministries are blocking this: valuable agricultural land must not be sacrificed.
An absurd argument if you take a closer look at the numbers.
Energy crops are currently grown on around 14% of the agricultural land in Germany. Intensively, with fertilizers, pesticides and subsidies. Mainly maize for biogas and rapeseed for biodiesel. The federal offices responsible for this sector are still raving about the CO2 savings that this would achieve. Such claims can only be made if the technological and economic developments of the last ten years are systematically ignored.
A new historical situation
Our hunger for energy cannot be satisfied with energy from the photosynthesis of plants. Wood was already becoming scarce in Europe in the 18th century. Industrialization and population growth were only made possible by the increasingly intensive use of fossil energy sources. Since 1770, the world's population has increased tenfold, and primary energy consumption has risen fortyfold. Now, however, we are faced with the task of very quickly stopping blowing fossil carbon into the atmosphere. The hope that we had found an alternative in nuclear energy has been dashed: hardly any new nuclear power plants have been commissioned worldwide since the end of the 1970s. Their share of electricity production has fallen from 17% to 10% since 1990. Electricity from new nuclear power plants costs more than from any other type of power plant.
In the 1990s, there were hopes of making better use of energy crops and thus replacing fossil fuels on a larger scale — at least temporarily. Government subsidies then triggered a boom in biogas and biofuels. But justified doubts quickly grew. From 2010 onwards, politicians began to put on the brakes in the face of tough resistance from agricultural lobbies. But once established, production continued. For years, the controversial debate has revolved around the alternative of "tank or plate". Food and nature conservation matter more, say the green ministers.
But the alternatives available have changed completely. New technologies have fundamentally transformed the situation compared to ten or fifteen years ago:
In terms of energy generation: photovoltaics can now convert sunlight into usable energy twenty times more efficiently than photosynthesis with energy crops. Thanks to unprecedented cost reductions in energy technology, photovoltaics is now the cheapest method of generating electricity.
In terms of energy use: Highly efficient batteries and power electronics now enable a much more efficient and flexible use of electricity. Electromobility and heat pumps enable huge efficiency gains compared to burning biomass.
This is not unknown among experts. Studies have been pointing out some of these aspects for years. But the combined figures are so staggering that politicians, business economists and interested laypeople do not trust them.
It therefore seems useful to present a few comparative figures in a readily understandable way.
Energy production
According to the Federal Office for Agriculture and Food (BLE), 168 petaJoules (PJ) of biofuels were consumed in Germany in 2020. Of this, 47% came from Europe and only 14.4% from Germany. Of the biofuels originating from Germany, 59% (14.3 PJ) were obtained from plants grown for this purpose, the rest from waste and residues. In Germany, rapeseed is primarily grown for diesel fuel. The Federal Statistical Office reports energy consumption of 2,253 PJ for all road transport in 2020. The area of land under biofuel cultivation in Germany therefore only supplied 0.63% of this.
According to the Agency for Renewable Resources (FNR), 2.35 million hectares (ha) of energy crops were cultivated in 2020. That is 14% of the agricultural area in Germany. Of this, 736,000 hectares (4.4% of the agricultural area) were used for biofuels, the rest mainly for biogas. The biofuel yield was therefore 19.4 GJ/ha. If all road traffic in Germany were to be powered by biofuels, this would require 116 million hectares. That would amount to 3.2 times the area of Germany or seven times the total German agricultural area.
If all road traffic in Germany were to be powered by biofuels, this would require seven times the available agricultural land
If, on the other hand, the area used for biofuel cultivation were to be allocated entirely to photovoltaics, this would result in an installed capacity of 590 gigawatt peak (GWp) (assuming a standard density of 0.8 MWp/ha). That would be almost three times the PV expansion target for 2030 (215 GWp). This would enable Germany to produce around 590 terawatt hours (TWh = billions of kWh) per year. This corresponds to today's total electricity consumption (583 THW). Or 42% of the electricity demand calculated by Fraunhofer ISE in its reference scenario for a completely renewable energy supply in 2045 (1,400 TWh). And that with an area that currently supplies only 0.63% of the energy consumed by road traffic!
In 2020, German biofuel cultivation supplied less than one per cent of energy consumption in road transport.
PV power plants could supply, on the same area of land, the whole of today's annual electricity consumption in Germany.
If this area were to be used for combined agriculture and electricity generation with agrivoltaics (assuming only 0.3 MWp/ha), the entire target for PV expansion could still be achieved.
These comparisons of magnitudes make it crystal clear that the current land use can no longer be seriously advocated.
However, it would not make sense to generate all the electricity required in PV power plants, even though this is now the cheapest technology. Firstly, in Germany it is advisable to produce around half of the electricity in wind power plants, as wind and sunshine complement each other well at different times. Biogas can also play a useful role in niches. Secondly, it is desirable to install a large proportion of photovoltaics on buildings or sealed surfaces, close to where they are used and in an environmentally friendly manner. However, Habeck is right: this will not happen as quickly and is (for the time being) more expensive than ground-mounted systems. The 11 GW of ground-mounted PV per year he is proposing would cover just under 14,000 hectares. This corresponds to only 0.6% of the area currently planted with energy crops, or 1.9% of the area misused for biofuels.
Use of electricity
If we now also look at today's possible uses of electricity, the madness of agricultural fuel production becomes even clearer. This is because electric motors are much more efficient than combustion engines.
The consumption data is 12 to 30 kilowatt hours per 100 kilometers (kWh/100km) - let's assume a generous average of 19 kWh/100km per car. With the electricity yield calculated above from the German biofuel cultivation area (590 TWh), 3,100 billion car kilometers could therefore be driven with electric cars, which is five times the car mileage in Germany in 2020 (626 billion km). In reality, 1363 PJ of energy was used for this mileage in 2020 - mainly with combustion engines - 95 times the German biofuel yield (14.3 PJ).
The electricity yield of PV power plants on the area now under biofuel cultivation in Germany would be sufficient for five times the mileage of cars in Germany if they were electric cars.
This frightening comparison can now be differentiated in one direction or the other. For example, that the production of rapeseed oil as a diesel fuel produces protein-rich rapeseed cake, which is used as animal feed. Or that solar power plants lock in land use for thirty years, while rapeseed or maize can be replaced by another arable crop in the next season. But also that the vegetation under newer PV power plants is much more ecologically diverse compared to intensive energy crop cultivation. The statistical data is also not always consistent — for example, the AGEE indicates a 16% lower use of biofuels than the BLE, which points to even lower efficiency. However, the orders of magnitude remain the same in all correction attempts.
For India, a renowned research institute came to similar conclusions, which it has summarized in the following chart:
Let's assume that Minister Habeck's plan to install 11 GW of ground-mounted PV power plants every year would be realized solely through re-purposing fuel monocultures. Then the annual reduction in biofuel production would correspond to the annual mileage of just 9,200 cars. In contrast, the additional electricity produced on that land would be enough for 4.3 million electric cars. Whether heavy private vehicles that are stationary 95% of the time are the last word in wisdom is another matter.
Minister Habeck's proposed annual increase in ground-mounted PV area is equivalent to the area used to grow biofuel for just 9,200 combustion engine cars, but could supply electricity for 4.3 million electric cars
We need to rethink more quickly in Europe. If we wait until the obstructionists have retired, it will be too late. Not only with regard to the climate crisis: Last year, China installed 45% of the world's new photovoltaic capacity and 59% of all electric cars sold worldwide. If you relate PV installations to gross national product, the EU only managed 44% compared to China, and Germany only 35%. Europe can no longer afford to waste time and resources. It's time to get serious.
A very very good text! Thanks!