Seeing the light: my conversion from fossil to PV8 October 2015
Maarten van der Burgt has had a distinguished career in the fossil fuel business, including over 30 years with Shell, and remains a world authority on gasification. However, he believes that the future belongs to solar PV, with electricity (via DC lines) and hydrogen (produced by electrolysis) the main energy carriers. A key influence on the evolution of his thinking has been his son Jaap van der Burgt, also an engineer, who worked for many years in solar cell manufacturing.
Most of my working life I have dealt with processes in refineries and the conversion of coal to liquids and power, where hydrogen plays a crucial role. This is also the case in my present work on solar power, which originates in the sun with the fusion of hydrogen into helium. Subsequently, in photovoltaic cells, this solar energy can be converted into electricity, which will become the most important energy carrier in a non-fossil future. Via electrolysis of water, electricity can be used to generate hydrogen and oxygen. Electrolysis will play a crucial role in a non-fossil and non-nuclear future where, in my view, hydrogen will become the second most important energy carrier. Hydrogen can be stored, eg, in depleted natural gas fields, and can subsequently be converted into electricity in fuel cells. Hydrogen can thus play a very important role in the large scale storage of energy. Moreover electrolysis of water is the obvious way to use surplus electricity and can serve to match supply and demand for power.
Liquid hydrogen will become the most likely fuel for large aircraft and for large fleets of buses and trucks and for large ships whereas electric cars are a good solution for distances of up to 150 km.
For intermediate size cars, ships and small aircraft, methanol and hydrocarbons are the most likely fuels. For the production of these fuels and for all organic chemicals, waste biomass will play an essential role. Such biomass, from, eg, forestry and paper and sugar mills, is our only source of "renewable carbon". These huge quantities of biomass can be converted to organic chemicals and top quality hydrocarbon fuels. Flash pyrolysis of biomass into bio-oil followed by gasification can supply us with synthesis gas, which can be used for making methanol, higher alcohols and transport fuels via Fischer- Tropsch synthesis processes. The gas from gasification can, as such, not be used for these syntheses because the hydrogen content is too low. Additional hydrogen from electrolysis can solve this problem and reduces the amount of synthesis gas from the gasification and therefore the amount of biomass required by about 50%.
If more biomass is required than available from biomass waste this could be produced in huge ponds of seawater in areas with a lot of sunshine. These ponds would preferably be located in desert areas in warm climates. A constant flow of salt water is required to avoid salt accumulation and facilitate harvesting. Fertilisers are not required.
Solar PV versus other power systems
I believe that expansion of solar PV is the only practical way to clean up our world and in particular our atmosphere as it is now pretty much certain that CO2 and to a lesser extent methane are the main culprits in bringing about anthropogenic climate change. PV solar in virtually all aspects scores better than all power generating alternatives - see Table 1.
Wind turbines are a nuisance in densely populated areas because of noise and intermittent shadowing. Furthermore, wind turbines make mince meat of millions of birds, bats and insects, not only on land but also birds migrating over the sea. Moreover the turbines require a lot of maintenance, and the problem is exacerbated when the turbines are located offshore.
In general, big hydro has major disadvantages in environmental and humanitarian terms. These can be avoided only when the turbines can use the diverted flow from nearby major waterfalls or can be installed very high in mountains where there is hardly any vegetation or wildlife. Nuclear has its well known problems and fossil fuel based power stations generate CO2 and indirectly methane from venting associated gas, ventilation gas from coal mining and leaking pipelines. Both fossil and nuclear generate a lot of waste heat that heats the atmosphere or rivers used for cooling.
Solar PV does not have any of these problems. Moreover it has no moving parts and does not require water for cooling and boiler feed water. Last but not least there are still enormous improvements in efficiency, manufacturing and cost reduction possible that no other technologies for generating power can claim.
Land use is sometimes mentioned as a particular problem for PV but it is also an issue for many other power sources, eg, when factors such as mining and the damming of rivers are taken into account.
As with many other power sources large scale energy storage is a problem. For domestic use low cost batteries can be used because weight is no limitation. An additional advantage is that this storage will reduce the load on the power grid. At the larger scale a technology such as hydrogen storage would be required.
Solar PV and HVDC
A way of alleviating the problem of intermittent sunshine is to deploy PV facilities over a large area and connect them with HVDC lines. Indeed, this combination of solar PV and HVDC could be seen as essential for the large scale success of solar power.
It is possible to transport electricity economically via HVDC wires over distances of up to 5000 km. The maps above aim to put this number into context.
To ensure reliable power production the PV power generation capacity needs to be substantially larger than the demand. Surplus power could be used for electrolysis of water to produce hydrogen for industrial use and for transport fuel. In this way the demand for power can be tuned to the supply. A second large consumer of surplus power could be the desalination of sea water. These big users of PV power should, wherever possible, be located adjacent to large scale PV power plants to avoid losses in converters and transformers.
It should be investigated whether one HVDC line of, say, 750 kV could be used to serve several areas by connecting them in series, for example three areas, each requiring 250 kV. Such a series network could reduce the need for transformers and DC/AC converters.
A big advantage of HVDC power transmission on land is that underground co-axial cables can be employed. This eliminates the need for pylons and suspended power lines, which, like wind turbines, are harmful to flying animals and also avoid visual pollution of the horizon.
All in all direct current will become more and more popular. Finally Edison will get his way, although we will still need some transformers. Small comfort for Tesla.
Basically all the technologies needed for the developments described above are available, but improvements are still being achieved in PV efficiencies.
In the area of solar cell production, much could probably be learned from the manufacturing of processors for the computer industry.
Grids need to be reconfigured to reflect the fact that that will be large numbers of small producers plus very large producers, with many more direct current networks.
Development work on batteries is well in hand but more work is required on improving the technologies for electrolysis of water and fuel cells. Further development work is also needed to improve techniques for growing of biomass in large ponds of seawater and for flash pyrolysis of biomass wastes.
The conversion from fossil and nuclear based power to solar needs to be fully supported by bodies such as the United Nations.
Rather than just subsidies, legislation is needed to make environmentally wrong decisions less attractive.
In my opinion we should stop building conventional power stations and move as soon as possible to solar energy via the kind of measures sketched out above, which I would regard as no-regret routes. I hope that decision makers can be convinced to act before one of the huge glaciers in Greenland and Antarctica slip into the ocean resulting in an almost stepwise rise in sea level.
First published in June 2015