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Supergrids revisited – but for desert wind not PV solar

By Dave Elliott

Dr Gregor Czisch is a pioneer for the idea of using long-distance supergrids to allow power from widespread sources to be traded across long distances, for example delivering renewable energy harvested in Africa to the EU. Unlike Desertec’s solar-based supergrid plan, his  supergrid plan, first outlined (in German) in 2001, focused mainly on using wind, which his modelling suggested was the best source. That idea has yet to be taken up and Desertec’s CSP/PV plan is also now defunct, but with solar PV costs now having fallen,  in a recent article Czisch  was asked if he thought it was now an option. However, he insisted that the results of his his original modelling still stood. He had factored in cost reductions for PV and found it wanting. So he still looks to wind, including power imported from North Africa, as a better bet. 

Czisch’s full scenarios  were published in English in 2011 by the IET, backing wind power.  In the interview he notes he had anticipated that, as PV moved down its learning curve, its costs would fall. He says it  was ‘not unexpected that the cost reduction per doubling of the installed power fell from 16% to just slightly more than 10%. This is well in the frame of cost reductions of technologies in a mature production state and could indicate that for PV the time is over in which it was a new technology with high techno-economic learning rates’.  So it may not continue for much longer.

Moreover  he argues that ‘ultimately, the cost of individual components is not the single criterion. The system as a whole must always be considered in case of the electricity supply. As long as a technology is not able to be used at all times and in a sufficient amount to produce the power required, its availability over time plays a significant role. This is well illustrated in my scenarios where I was looking for the most cost-effective way to provide an electricity supply for Europe and its neighbours utilizing renewable energies only. This was achieved by means of mathematical optimization, not least to achieve results having the greatest possible objectivity. In the basic scenario, the costs of photovoltaics were calculated at 5,500 € per kW rated output. The result of the optimization was that PV should not be used since there was no solution to the supply problem in which PV could provide a cost-reducing economic contribution. The most favourable system with which electricity can be supplied significantly below today’s electricity costs in Germany proved to be a strong transnational electricity grid system combining wind energy, hydro power (as used at the time the scenarios were calculated), and energy from biomass used sensibly. However, due to the continuing trend of high cost reductions for PV systems, these results could not be simply left unquestioned. It was therefore valid to assess how lower PV costs might change the situation and so scenarios assuming reduced PV costs were also calculated’.

He reports that: ‘In successive halving steps, all of the costs of PV systems were reduced and new scenarios were calculated; whereby somewhat optimistic estimates for their service and maintenance costs were used. However, reducing costs of PV down to and including a quarter of the initial costs (already well below current costs), the result remained the same. That is, as before, PV still could not make a cost-saving contribution. An improved result was only obtained following the third halving of the costs to one-eighth of the initial costs. In this case, PV was able to make a small cost-cutting contribution by utilizing it only in the southernmost African regions of the supply area. (The whole supply area in the scenarios reaches from the southern Sahara-states including Scandinavia in the north and from the Atlantic in the west until West-Siberia in the east.) Overall, this resulted in the electricity supply cost being reduced by a negligible 0.8% compared to the base case scenario. According to this scenario, the electricity was sent from the southern outskirts of the Sahara and from Egypt via specially built power transmission lines to the consumers in Europe. However, we are still a long way off from achieving these projected PV costs, and thus it remains uneconomical to use PV in less sun-drenched regions like Europe. Even a further halving to a 16th of the initial costs (roughly one-sixth of today’s costs) did not fundamentally alter the situation. Although this scenario made use of PV in regions on the European Mediterranean coast, it did not reach more northerly regions such as Germany or Scandinavia. Even though the calculations arrived at costs of the photovoltaic generated electricity already well below the average electricity generation costs in the scenario area, the total proportion of PV in this scenario was relatively small. The production cost reductions of just a few percent compared against the basic scenario were rather poor.’

So PV was not going to be very viable for supergrid use, and using it locally, in the EU, had limited value, given its lower intensity level and higher variability. That was the case even with energy storage: while hydro pumped storage could help, he was dismissive of most storage options, including P2G hydrogen, especially for longer term balancing. They were too expensive, inefficient and limited compared with long distance supergrid trading of surpluses. And he insists that wind is better for that than solar CSP or PV, as he claims the Desertec group eventually found.

It is usually assumed that the solar resource in North Africa is vast, more than any other renewable resource. But, Czisch says, the wind energy potentials in the North African deserts are so large that it is practically impossible to even come close to exhausting them. Eight of the North African Sahara countries have each a wind potential that is more than sufficient to produce the amount of electric energy that the entire EU and the whole of Africa require’. So there was no risk thatAfrican countries will be deprived of their natural wealth if one is to promote renewable energy exports’. There was plenty for all.

Clearly Czischhis modelling suggests that his mainly wind-based supergrid is the cheapest option and is dismayed that Desertec had headed off in the wrong direction, while the ‘decentralist’ greens opposed supergrids of any sort.  So we were now faced with what he sees as a high cost local ‘self-generation’ approach in Germany and the EU generally, the cost of which has provoked a political backlash and cuts. He sees it as getting worse, with expensive storage and new local distribution links being required for balancing, pushing up the cost faced by the system and hence overall consumer costs. All in all, a dramatically opposed view to that promoted by decentralists like the late Dr Herman Scheer in Germany and by PV solar enthusiasts like Professor Keith Barnham in the UK.

Czisch may be too dismissive of local solar use. Roof-top PV can deliver power direct to users without transmission losses and it is well matched to day-time summer air con demand: see my recent posts – it’s a good decentral option.  Nevertheless, while there may be problems with supergrids, quite apart from the major trans-border political issue they open up, they might offer valuable access to some balancing capacity with low HVDC transmission losses. For the moment, however, as my next few posts will indicate, most countries are focusing on internal energy balancing, with limited power imports/exports – international supergrids may have to wait.

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