On February 1st at 6.15 am the wind farms operated with a temporary capacity of 7,677 MW. It was a record. Renewables will break more records like this, and PSE (Polish grid operator – ed.) predict that this will cause reductions at the operator’s request until the grid is able to absorb more renewables – writes Wojciech Jakóbik, editor in chief at BiznesAlert.pl.
Troublesome RES record
In January of this year, PSE has already had to reduce the generation of wind farms twice, due to excess generation in the system. BiznesAlert.pl reported that on New Year’s Eve last year, wind power in Poland reportedly provided so much energy that the operator Polskie Sieci Elektroenergetyczne (PSE) had to ask power producers from this sector in advance to limit capacity. This was necessary for security reasons. Energy demand on December 31, 2022 was at record low, and conventional units were operating at a minimum of close to 5 GW, there was an emergency export of energy. It wasn’t enough. PSE recommended reducing wind farms capacity by 1,200 MWh on December 31 and 23,400 MWh on January 1. PSE confirmed that on the 1st of February at 6.15 am wind farms operated with a temporary capacity of 7,677 MW, the previous record was 7,600 MW on January 4 this year. February 1st also set a record for hourly production. Between hours 6 and 7 the turbines produced 7603 MWh of electricity. The previous record was set on January 4 and was 7,576 MWh.
Considering the dynamic growth of wind farms and photovoltaic power in recent years, this situation will happen again. However, the excess of RES and the periodic need to reduce it entail compensation costs that are covered by all domestic electricity customers. There is nothing wrong with reducing power generation for which there is no demand, but it needs to be understood that such actions increase the costs of RES integration. The solution may be to increase the flexibility of power plants and customers, as well as invest in energy storage or other forms of surplus management. PSE calculated that the daily generation of RES periodically exceeded 40 percent of national demand, or 174 thousand MW during the day. According to PSE data, RES capacity will only grow. Onshore wind capacity is expected to increase from 7,302 MW to 14,936 MW, offshore wind farms are expected to provide 8,389 MW in 2030, but currently generate nothing. Photovoltaic power is expected to increase from 7,780 MW to 22,123 MW by 2030. According to PSE, the RES potential is expected to reach 100 TWh in 2030, or 50 percent of annual consumption in Poland.
Currently, there is no way to manage the surplus of renewable energy generation in the system. If customers at home or abroad are not interested in receiving this energy and there is no other technical possibility of using it, there is no other way out but to reduce renewable generation. This is especially true for wind farms, which, unlike prosumer distributed PV, are much larger, better monitored and controllable installations. With the progress of technology, especially in the area of electricity storage and its conversion to other energy carriers, this situation may change. At this point, it should be mentioned that RES are weather-dependent, and conventional power plants need to adjust their work to their variability. While on New Year’s Eve there was a record production from wind turbines in Poland, in January 2022 there was a Dunkelflaute and there was no wind, which meant the generation dropped to a record low. Coal-fired power plants are not prepared for such fluctuations.
The system has a technical minimum in terms of the number of power plants ans capacity needed to maintain technical parameters, such as frequency. According to PSE, this minimum is estimated at between 9,000 MW in the winter and 7,000 MW in the summer. This is a minimum that needs to be produced by large system power sources (Centrally Dispatched Generating Units) and dispersed combined heat and power plants and industrial facilities (Non-Centrally Dispatched Generating Units, NJWCD). The latter are not subject to the operator’s instructions, so they are not taken into account as a sure bet when it comes to maintaining the necessary capacity. If generation is high and demand is low, as on New Year’s Eve 2022, energy prices begin to fall to negative levels. This is a signal from conventional sources that they can not switch off for fear of their viability. For example, PSE calculates that 200 MW coal-fired units require 7-10 start-up hours and have a technical minimum of 20-40 percent capacity. They also change the load slowly, so unlike RES, they are not flexible. Among other things, the 200+ Units Program, which extends their life, is supposed to answer this challenge, provided that their contractor Rafako, which is on the verge of bankruptcy, is available. It is also not possible to export to other markets if there are also surpluses there, and they, are often correlated with each other, due to similar weather conditions, for example in Poland and Germany. The surplus must therefore be reduced by the operator at the cost of the energy customers in the PSE tariffs. The more RES there is, the greater the scale of these challenges.
“We are approaching a 20 percent share of renewables in energy production. This growth is mainly attributed to photovoltaic farms, whose capacity is growing every month. We have already added to the system about 12,000 MW in terms of photovoltaics and more than 9,000 MW in the case of wind farms,” calculated Konrad Purchała, Director of the Grid Management Department at PSE.
The maximum quarter PV generation exceeded 6700 MW. The maximum quarter generation from the wind exceeded 7,600 MW. Such capacity is usually a great support for the system, complementing the power balance very effectively. However, periods with low customer demand, such as weekends and holidays, and night hours, are challenging. System power plants cannot be completely turned off, because their work is necessary to ensure stable operation of the system and compliance with its technical parameters. “On the night of January 31, despite the record generation of wind farms, we did not have to limit their work, but it was necessary to take other measures to balance the system,” admitted Konrad Purchała from PSE when commenting on the record wind power production exceeding 7.6 GWh. Wind farms accounted for a third of the country’s electricity production at the time.
“Renewable sources are a very good complement to the power balance, but their output depends on weather conditions. Ensuring the continuity of electricity supply to customers at the level required by modern society requires disposable and controllable generation capacities, which today are reserve, conventional capacities,” Konrad Purchała said. “The replaceability of some renewables with others is unfortunately too low to maintain supply continuity. If we want to be confident at the level required for a dynamic economy, we need to have reserve resources that guarantee the ability to meet demand even in periods of climate drought, i.e. when the wind does not blow and the sun does not shine,” he added.
The main tool for balancing the system is the wholesale market. If market participants fail to ensure a balance between electricity demand and electricity production from the market, the operator is obliged to adjust the power balance. If there is excess energy in the system and it is not possible to use it in any other way, the operator must take additional measures. Among them is interference in the supply of energy, as happened in the case of reducing the generation of wind turbines on the New Year’s and New Year’s Eve. “Market participants do not always make decisions in line with the needs of the system, which often leaves us with a large imbalance and oversupply of energy during periods of high generation from renewable sources and low demand,” admits the representative of PSE.
In such situations, we lower the generation as much as possible. When we have too much unused energy in the system, the generation at conventional units is the last resort. We launch energy storage pumps in hydroelectric power plants and we try to agree on non-market inter-operator exports. However, these measures can sometimes prove insufficient, because lowering the capacity of or shutting down power plants is not always possible for technical reasons, and when there is high wind generation in Poland, neighbors often also face problems of excess generation and do not want energy from Poland. Then the only available tool is the emergency export and limitation of the generation of RES. In accordance with the regulation of the European Parliament and of the Council on the Internal Market in Electricity, the use of non – market reduction of RES for balance sheet reasons is subject to financial compensation-in practice, PSE covers the reduced revenues due to unproduced energy and property rights. The funds for this purpose come from the revenues from the operator’s transmission tariff and are therefore borne by all national electricity customers.
Waiting for the reserve
Thus, until the conventional reserve increases, the development of RES can be limited by systemic barriers. Coal, which works in the base and is not flexible enough, is to be replaced by nuclear power, but only in the 2030s. Gas-fired power with greater flexibility must be limited for safety reasons. This means that the days in which the wind turbines sit still will happen more and more often. How to handle this The operator believes the solution lies in incentives for customers to change energy demand depending on prices, as well as market incentives for generators to limit generation themselves in situations of excess energy in the system. Flexible conventional sources, new or upgraded, as well as energy storage or electrolysers would also help.