In well-insulated houses, a heat pump is sufficient to provide hot tap water and heating. Electrical resistance wire heating is used to provide additional heating capacity for short periods of cold. This approach saves on the provision of infrastructure to supply natural gas, but it means that far more electrical substations and underground power cables are required. In coming years, 10,000 workers will be required just to lay the needed cables and carry out the associated excavation work. “We think that the problem can be solved by using SmartGrid technology such as the PowerMatcher software”, says Olaf van Pruissen of ECN Efficiency & Infrastructure. “Fewer workers would be required for excavation work and the high costs of additional substations and cables would be avoided.”

A project developer gave energy company Stedin a shock in 2008 with a development plan. The plan envisaged 1400 free-standing houses that would not be connected to the gas network. Instead they would only use electrical power to drive a heat pump and, when required, provide additional heating. This added up to a peak power of 10 kW per house. This development in Hoogdalem in Gorinchem meant that Stedin would have to build not 4 but 22 substations as well as entailing costs for an additional transmission medium voltage line and higher capacity underground cables. “Stedin came to us to ask whether we knew of ways to prevent peaks in demand while taking the comfort of the residents into account,” explains Olaf van Pruissen of ECN Efficiency & Infrastructure. “We used a simulation to show that the additional substations and associated cables were not absolutely necessary, while the residents’ comfort was hardly affected.”

Heat pump plus resistance heating requires many additional substations, cables and transmission lines

Energy companies have a duty to supply electrical power. This means that they must be able to supply sufficient power to their customers at all times. This also applies in the case of a so-called ‘black start’ after a serious power outage (for example, in the event of a helicopter crashing into the power lines in Bommelerwaard in the Netherlands leading to a 48-hour outage). Van Pruissen: “A black start after a long outage like that is a nightmare for any power company. In a residential area such as the one in Hoogdalem, in each house the heat pump will switch on (2.2 kW) in every house simultaneous with the electrical resistance heating (6 kW) to warm the cooled house up again. A normal substation and cables would not be able to handle this. The substation would melt and/or the underground cables would fail. Of course, the safeguards would cut in to prevent damage, but this would be at the cost of the customers’ comfort: all the houses would be dark and cold again.”

Chart of the power needed from a power grid with (green) and without PowerMatcher control. The grid operators are quite apprehensive of this peak load in the start (llustration ECN, click to enlarge).

This scenario is not acceptable. This is why the energy company lays additional cables and builds substations to be able to handle exceptional peak loads. This costs a lot of money, which, in the end, has to be paid by the customers of the grid operator. “For this specific project in Gorinchem involving 1400 houses in the Hoogdalem neighbourhood, these costs amounted to roughly 1.5 million euros,” says Van Pruissen. “In a simulation of 100 houses, we were able to demonstrate to Stedin that the use of PowerMatcher technology would enable the impact on the standard electrical infrastructure to be reduced significantly with little impact on the residents’ comfort.

Smart Proofs
Grid operators are worried about peaks in power demand. In addition to the black-start problem, the idea of a sudden cold spell during the last weekend of the winter sports holiday gives them the shivers. In this case, all the thermostats in all the houses would command to switch on all heating device early on Monday morning and demand the maximum power from the power network. Is ECN able to circumvent these peaks using its PowerMatcher technology? And, what would the consequences be in terms of comfort for residents in Hoogdalem?
Stedin and other grid operators were initially very sceptical that intelligent control would be able to deal with the peak demand problem. “To allow grid operators to actually experience how the technology works, I let them participate in the PowerMatcher game.” This is a kind of role-playing game in which the players make choices regarding the use of money, hardware and certain device controls, the aim being to supply power to customers. Van Pruissen: “The game gives the players a better understanding of how SmartGrid works. Every time it is played, it creates better understanding and goodwill.”

Couperus
Within the framework of the Smart Proofs project, partly financed by Agentschap NL, ECN was able to use the building model of the houses in Hoogdalem in a simulation. This allows Van Pruissen to simulate many different circumstances, including Stedin’s two nightmare scenarios. [Show picture 6.7 from the report.] In this scenario, PowerMatcher intelligently matches the power demands to the available network capacity. “Much more can be achieved this way than one might expect,” says Van Pruissen. “If one permits houses to heat up again in, for example, 90 minutes rather than 60 minutes, it is possible to drop 60% of the power network capacity without any problems. If one accepts an initial room temperature of 19° instead of 20° C, one can even drop 70% of the capacity.”

PowerMatcher technology enables a major cut in electrical power usage with little impact on the resident's comfort: if heating up may last 1,5 time longer, a neighbourhood could do well with 60% less electrical power (Illustration: ECN).

Implementation of the development plan in Gorinchem should have begun in 2010, but the plan has been put on hold because of the financial crisis. However, the Smart Proofs simulation for Stedin was not for nothing. Recently, it was announced that Stedin has approached ECN to apply the PowerMatcher technology in the Smart Grid Couperus pilot project [include link to related news article] in the province of South Holland, in which Eneco, ITHO and Ceres/Vestia will also participate. Van Pruissen: “The project concerns a complex of apartments. The heat pumps are smaller and the probability of the electrical resistance heating switching on simultaneously is lower, because the residents have to press a button first, which means that the impact of PowerMatcher on the infrastructure is less high. Nevertheless, the partners in the project are very interested in starting this project.”

Heating and cooling
In more southerly and, thus, warmer areas, there are other challenges: namely air conditioners. Van Pruissen: “Brazilian researchers report that there are often power outages in São Paulo on summer afternoons. The large number of air conditioners in the city demands more power than the power network is able to provide and safeguards cut in and switch everything off. Their plan is to create a cooling buffer, to distribute the electrical load more evenly. The idea is that the air conditioning units in office buildings and shopping centres would continue to work at night. During this time, the units would cool insulated tanks of ice, water or certain salts. During the afternoon, this buffer would provide the additional cooling capacity for customers so that the power network is not overloaded. The PowerMatcher technology would be an excellent alternative to this approach.”
As far as PowerMatcher is concerned, it does not matter whether the load is due to electric resistance heating or air conditioning units, as the objective is to make the most efficient use of electricity. Brazilians or – closer to home – Italians and Greeks, who would like to play the PowerMatcher game, would be welcomed by Van Pruissen.

Contact
Olaf van Pruissen
ECN Efficiency & Infrastructure / Power Systems & Information Technology
Tel.: +31 (0)22 456 81 24
E-mail: Olaf van Pruissen

Information
High concentrations of heat pumps in a neighbourhood and the consequences for the power network

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