Alternatives to the replacement of an electrical heating system
The aim of this master thesis project is to make an energy survey for a groupof apartments and suggestions to change the heating system from electricity to a moreefficient one. There are in total 73 flats in 21 buildings. All flats are separated in severalhouses from two to five flats in one building. There are two different kinds of flats. Onewith three rooms in one floor, in the following referred to as ‘flat A’ and the other onewith four rooms in two floors, in the following referred to as ‘flat B’. In the area there are also two buildings for the commonalty. In these buildings there are ashelter and several common rooms like a storage and a laundry. In our work these twobuildings are not included because they are used by everyone inside the community andwe could not obtain exact values for the used electricity and the water consumption. Soour work is specialised only on the residential houses.The first part of this thesis contains the energy balance for the different kinds of flats tosee how much energy they consume for heating and hot tap water. To get theses valueswe have to analyse the total energy flow into one flat and compare it with the energywhich is used because of transmission losses, ventilation losses, hot tap water, electricityfor the household and natural ventilation and infiltration.The total energy consumption for flat A is about 19000 kWh per year and in flat B about23200 kWh per year. But the electricity which is used and has to be bought is about15600 kWh per year in flat A flat and 17600 kWh in flat B. The rest of the energy is fromso called free heat caused by solar radiation and internal heat generation. These numbers for the electricity need in one year create annual costs of about20000 SEK in flat A and 22500 SEK in flat B. To reduce these costs it is necessary toknow where this energy goes and for what it is used.The important parts of the energy balance for this thesis are the transmission losses, thelosses caused by natural ventilation and infiltration and the used energy for hot tap water.The losses caused by mechanical ventilation have also a significant value, but they wouldonly affect the new heating system if the ventilation system would be connected to thenew system. And the electricity used in the household for electrical devices can only bechanged by the consumer himself. The part which is affecting the energy costs for thetransmission and natural ventilation losses and the hot tap water sums up to 9240 kWh peryear in flat A and flat B. This causes costs of about 10000 SEK per year.To reduce these costs it is necessary to change the actual heating system. In the followingwe analyse the saving potentials with a change to an air-water heat pump or with aconnection to the local district heating network.The costs which can be saved with the installation of a heat pump sum up to about7000 SEK per year. The installation costs are about 100000 SEK to 125000 SEKdepending on the different proposed models. If you consider that the existing electricalboiler has to be changed anyway in the next years the investment costs for thecombination with a heat pump decreases. The payback time is then between 9½ and13½ years. With assumed increasing electricity prices of 5 % each year the payback timedecreases to 8½ to 11 years.With a connection of each flat to the local district heating network the energy costs forheating and hot tap water decreases to 3200 SEK per year. Although the price per kWh fordistrict heating is much lower than for electricity the costs are not decreasing a lotbecause of a high annual fixed fee of 7100 SEK. The saved money per year sums up to300 SEK and 1000 SEK depending on the electricity contract. The payback time for thisalternative is between 50 and up to 160 years.An alternative to the exchange of the heating and hot water system is to change the actualheat exchanger of the ventilation system. With this measure the energy consumption canbe reduced with less investment costs. The investment costs for a new heat exchanger areabout 35000 SEK, including a new exhaust hood from the kitchen outwards to reduce thecontamination of the filters in the heat exchanger. The payback time ranges from 13 years in flat A to 21 years in flat B.
School:Högskolan i Gävle
Source Type:Master's Thesis
Keywords:heating system heat pump district energy balance
Date of Publication:10/17/2008