Effekten av effekten. Elanvändning och laststyrning i elvärmda småhus ur kund- och företagsperspektiv. Fallstudier

Sammanfattning: Electricity must be produced at the same time as it is used. This necessitates flexibility in the electricity production and electricity networks. Until recently, the increase in electricity demand and peak power demand has been met by expansion of the electricity production. Today, due to the deregulation of the electricity market, the production capacity is decreasing. Therefore, there is a national interest in finding solutions to peak problems also on the demand side, i.e. enabling electricity users to decrease or shift load when needed. For local players in the electricity market, there are various technical and economic motives for developing methods to influence or control customers’ usage patterns. In the studies described here (Study 1 and Study 2) ten households in electrically heated houses, were examined. The households were all customers of the electric utility Skånska Energi AB. In 1999 the utility equipped their customers with a remote metering system (CustCom) that has an in-built load control component. A large number of studies, in Sweden as well as in other countries, investigate the impact of habits on energy use within a home. A hitherto not investigated area is the effect of habits on the load pattern. In Study 1 (of this licentiate thesis), the load pattern of ten households was examined by using energy diaries combined with frequent meter readings (every five minutes) of the load demand for heating, hot water service and domestic electricity use. Household members kept energy diaries over a four-day period in January 2004, noting time, activities and the use of household appliances that run on electricity. Comparison of the data from these two sources provided an estimate of the impact of various activities and the use of electrical appliances on load demand. The analysis showed that the use of heat-producing household appliances, e.g. sauna, washing machine and dryer, appliances used for cooking (oven, kitchen range-hob, electric kettle and microwave oven), dishwasher and extra electric heaters, contribute to the household’s highest peaks. Turning on the sauna and at the same time using the shower equates to a peak load of 7-9 kW. This, in addition to the use of electricity for heating and lighting along alongside electricity use for refrigerators and freezers, results in some households reaching their main fuse level (roughly 13,8 kW for a main fuse of 20 A). This means that the domestic use of electricity makes up a considerable part of the highest peak loads in a household, but the highest peaks occur together with the use of electricity for heating and hot water. vi ix In the second study, Study 2, the households participated in a load control experiment, in which the utility was able to turn on and switch off the heating and hot water systems remotely, using the CustCom system. Heating and water heaters were switched off for periods of 1-4 hours (except for one occasion during which the water heater was switched off for 16 hours) without letting the households know when the control periods would take place or how long they would last. Household heating and hot water comfort as well as the households’ attitudes towards and experiences of being controlled were investigated using a combination of methods. During the experiment period, which lasted three weeks, the household indoor temperature was measured to establish the temperature drops caused by switching off the heating system. The households were asked to make notes of their experiences of thermal comfort and hot water comfort on a specified “comfort sheet”. In order to be able to ascertain whether the households had missed out on any of the control periods, the household members had to keep a record of when they were away from home. Following the test period, interviews were carried out in order to establish the household experiences of the load control experiment, to gain insight into the household members’ views of their energy use and energy habits, and to gain an understanding of the requirements that customers have regarding load control measures. Issues such as limitations of control time, compensation and feedback were discussed. Also, a more indirect form of load control - tariffs - were discussed, namely classical time tariffs and tariffs using a peak load component where the grid fee is based on an average of the customer's three highest hourly peaks during one month. Interview data, records of thermal and hot water comfort and indoor temperature readings showed that the households noticed some of the control periods but that equally some went unnoticed. At its lowest, the indoor temperature went down by 2,5ºC. Obviously, longer control periods of three or four hours contributed to larger temperature drops, but at the same time sun radiation through windows affected the indoor temperature. Hence, the households seemed to be more sensitive to load controls in the mornings than in the evenings when the sun had had the chance to heat up the house. The households under investigation kept different indoor temperature levels; the average temperature ranged from 18,5ºC to 24ºC. Intuitively, a household that normally keeps a lower indoor temperature should be more sensitive to a temperature drop of a couple of degrees. In this study, however, the households with a higher average indoor temperature tended to sense the temperature drops to the same extent as those with lower average indoor temperatures. This may be a result of these households adapting their clothing to the high indoor temperature by for instance wearing Tshirts or walking around barefoot even in wintertime. Another factor impacting on the thermal experience is the speed of the temperature drop. Houses equipped with direct resistive electric radiators and light frameworks lack the capacity to store heat and as such the indoor climate will be affected more easily. Load control of the hot water systems went unnoticed. Only one household experienced a shortage of hot water when the water heater had been switched off for several hours (during the 16-hour long control period). The other households did not notice the switch-off period at all. This may however be a result of the fact that the households participating in this study did have big water heaters in relation to their hot water needs.