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5 The Role of Copenhagen in a 100% Renewable Energy System

5.4 Heat saving potential in The City of Copenhagen

5.4.2 The potential heat savings

In this report, an extract from the heat atlas was made for The City of Copenhagen and compared to the rest of Denmark. In Figure 46, the overall saving potentials for scenarios A, B and C are presented for both Denmark and The City of Copenhagen. The scenarios are based on the aim

of reaching target U-values for each building improvement. All types of building improvements are implemented to certain degrees for each scenario and do not take the building periods into account, unless the target U-value is reached. This means that the same type of building improvements are carried out in each scenario, but scenario C implements more than scenario A.

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Figure 46: Comparison of heat demand saving scenarios between Denmark and Copenhagen.

It is clear that the saving potential in Copenhagen is higher than in Denmark as a whole, which is due to the difference in the building stock. Scenario A has a potential of saving 56% in The City of Copenhagen and 53% in Denmark as a whole, and scenario C has a potential of saving 79% in Copenhagen and 74% in Denmark.

The heat atlas used in this report is based on an extract from the BBR from April 1st 2013 with data updated on December 5th 2012. Buildings constructed after this period are not included in the analysis.

In some buildings, it is not possible to make energy renovations due to building protection, high existing standard, or the lack of information in the BBR. Therefore, the initial step in the analysis is to choose the share of the buildings where heat savings are an option. Choosing all buildings from the heat atlas where heat savings are possible

gives a list of 48,591 buildings with a total heat demand of 4.8 TWh/year in The City of Copenhagen.

5.4.2.1 Investment costs related to implementing heat savings

Implementing scenarios A and C for all the chosen buildings gives the investment costs shown in Figure 47. If Scenario A is implemented in all buildings, heat savings would be 2.7 TWh/year, while implementing Scenario C would result in savings of 3.8 TWh/year. There are two types of costs for each scenario, the direct costs and marginal costs. As mentioned before, the direct costs are the costs for implementing heat savings with the sole purpose of energy renovating buildings, while the marginal cost is the cost associated with implementing energy renovations when the building is renovated anyway.

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Figure 47: Investment cost of full implementation of scenarios A and C in The City of Copenhagen.

It is clear that the marginal costs correspond to about half of the direct costs. Additionally, it is clear that there is a difference in costs where the cheapest buildings have a marginal saving cost below 10 DKK/kWh and the more expensive

buildings above 15 DKK/kWh. This means that a 56% reduction can be achieved through all four strategies. The accumulated costs of this are shown in Figure 48.

Figure 48: Accumulated investment costs where “56% in all” represents scenario A and “79% in cheapest” represents scenario C.

It is important to notice that there are two overall strategies which both achieve the same level of annual heat savings. The first is to improve all buildings to the same level, while the second is to

only improve some of the buildings but to a higher level. The reason for choosing the latter is that some buildings are more expensive to renovate than others as shown in Figure 47. Figure 48

47 illustrates that the cheapest option is to partly

implement Scenario C to achieve 56% savings and use marginal costs. It is, however, close to the cost of implementing Scenario A in all buildings to achieve 56% savings. As a large share of the buildings in the municipality has similar costs, choosing between strategies does not influence the total investment much. The more important point is that the use of marginal cost greatly reduces investment costs. This means that for the individual building, the strategy should be to implement energy renovations when the building

is to be renovated anyway. Even though the investment costs are almost the same for both scenarios, choosing either of them will make a difference in terms of where the heat saving is placed geographically. In the following section, geographic representations of the heat savings are presented in the form of maps.

5.4.2.2 Heat saving potentials

A geographic representation of the heat saving potential is shown in Figure 49 for Scenario A.

Figure 49: Heat saving potential for each district when implementing scenario A in all buildings.

The heat saving potential is highest in the inner city areas, which is due to a combination of the age of the building stock and the building density within these areas. Comparing scenario A and scenario C shows that in the latter, a larger part of the heat savings is allocated to the buildings with the lowest implementation cost. This is mainly because the buildings with the lowest heat saving cost are not geographically evenly distributed;

thus, in some areas there are more of these buildings. Also, it does not seem like there is a pattern in regard to where the cheapest buildings are placed; it is both in central city areas as well as areas further away from the city centre.

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48 5.4.2.3 The heat demand before and after

implementation of heat savings Implementing Scenario C with 79% in the cheapest buildings, thus reaching 56% accumulated, would be the cheapest solution. However, it must be underlined that the difference between this and implementing Scenario A in all buildings is not significant. The maps include the demands of buildings where no heat savings are implemented.

In Figure 50, the present demand is shown as annual heat demand in the buildings within each area. The present figures show that the demand is largest in the city centre, but also that many other areas have large annual demands. In Figure 51, the heat demand after implementing heat savings is illustrated. This shows that most areas have changed to lower categories, giving a map with mainly green areas.

Figure 50: Heat demand before implementing heat savings in The City of Copenhagen.

The result is basically as it could be expected, since the scenario reduces the heat demands significantly compared to the present level. From a heat supply side, it is also useful to see what the heat density of each area is before and after

implementing the heat savings, as this will influence the technical design of the future supply system. Therefore, the heat demand given in kWh/m2 is shown in Figure 52 and Figure 53.

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Figure 51: Heat demand after implementing heat savings in The City of Copenhagen.

Figure 52: kWh/m2 before implementing heat savings.

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Figure 53: kWh/m2 after implementing heat savings in The City of Copenhagen.

As in the previous maps, more areas turn green when implementing savings, suggesting that the heat demand density is lowered. With the current heat demand, most areas have a heat demand density of 35 kWh/m2 and in many of the inner city areas it is higher than 75 kWh/m2. After implementing the heat savings, almost all areas have a density below 75 kWh/m2. This also means that it will be a good idea to coordinate energy renovation in buildings with the renovation or replacement of district heating pipes, as the existing pipes can be replaced with pipes of smaller dimension if none of the buildings require high forward temperatures.