Grid expansion for strong solar power growth: technically feasible, costs manageable
Modernization of the low voltage grids to accommodate 55 gigawatts of solar power requires investments totaling around one billion euros by the year 2020 – an amount equal to the annual costs of retrofitting the distribution network, which the low voltage grid is part of
An investment of 1.1 billion euros is needed to expand the low voltage grids so that they can absorb 55 gigawatts of solar power capacity by 2020. Taken together with the solar power that is fed into the medium and high voltage grids, this would mean that 70 gigawatts of solar power could be available in Germany – a capacity that would cover ten to twelve percent of Germany’s electricity demand. This is the result of an expert report by the consultancy firm Ecofys, conducted on behalf of the German Solar Industry Association (BSW-Solar).
“From a technical standpoint, this expansion can be easily integrated into the ongoing process of network renewal,” explains Jörg Mayer, Executive Officer of BSW-Solar. The routine costs for renewing the distribution network amount to one billion euros per year. “That means that the expansion requirements for solar power amount to only one tenth of the annual retrofitting volume. The costs,” according to Mayer, “are clearly manageable.” The added cost factor for an average household would amount to 11 cents per month.
“This shows that there are no significant obstacles, neither in terms of cost nor from a technological standpoint, to a continued robust expansion of photovoltaics. Whoever claims otherwise is speaking out of prejudice,” says Mayer. The costs for the further expansion of photovoltaics, he goes on to explain, have become negligible. “It is imperative,” according to Mayer, “that the political establishment make an unconditional commitment to a strong expansion of solar power and that it forgoes excessive cuts in the support for solar power.”
The production of solar power is for the most part decentralized, as it takes place in immediate proximity to consumers – for example on their own rooftops or in local commercial enterprises. This is why 80 percent of solar power output goes into local low voltage grids at the municipal level. The so-called distribution network is made up of the low voltage grids, the medium voltage grids, which nearly all photovoltaic systems feed into, as well as the 110-kV grid. The low voltage grid of the Federal Republic of Germany currently comprises a total of 1.1 million kilometers of power lines.
In order to enable the future feed-in of up to 55 gigawatts of solar power capacity into the low voltage grid, there are two primary areas where modernization is necessary. Firstly, additional low voltage power lines must be installed. Secondly, controllable distribution transformers should be employed, which can react flexibly to electricity output and solar power input.
“The primary factors driving the costs are the earthworks required to lay new underground cables and the installation of modern transformer stations where they are needed,” explains Bernhard Hasche of Ecofys. “Since such cut-and-cover line construction is similar to the work done in the telecommunications sector, there should be no acceptance problems among the population. For the most part, the lines for solar power already exist beneath the sidewalks.”
The use of controllable distribution transformers helps reduce the overall costs of expanding the low voltage grids. “The same applies to the use of so-called reactive-power-capable inverters, which help balance out unwanted voltage rises and dips in the grid,” says Thomas Stetz, network expert at the Fraunhofer Institute for Wind Power and Energy System Technology (Fraunhofer IWES). The research institution examined, within the framework of a preliminary study, the technological possibilities for the network integration of photovoltaics. As of 1 January of this year, inverters capable of reactive power are mandatory for all new PV systems, with the exception of the smallest systems. According to the Ecofys expert report, these inverters are capable of reducing the photovoltaic-related network expansion in the low voltage grid by 60 percent.
But what does this mean for the consumer in concrete terms? The expansion of the low voltage grid, costing 1.1 billion euros to 2020, would bring about an increase in network charges by 0.4 percent. As a result, the average household, which consumes 3500 kilowatt hours of electricity per year, would have an added cost equivalent to 11 cents per month.
“In order to make the transformation of the energy system work, we can and we must turn the distribution networks into a kind of collection network for decentralized electricity,” demands Prof. Dr. Bernd Engel, network expert at Braunschweig Technical University. “Not only solar power, also biomass, combined heat-and power (CHP) and hydro-electric power plants feed in significant portions of their capacities into the low voltage grids.”
“It’s apparent,” as Jörg Mayer concludes, “that the retrofitting of the low voltage grid, which is necessary to accommodate large volumes of solar power, is technically viable and achievable at manageable costs.”
For further information (german) please find studies and presentations enclosed to the german press release.
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