By Frede Hvelplund, Dr. Techn. Professor in energy planning, Aalborg University
In this article, we will compare the costs of energy conservation in multifamily apartment buildings with the incentive system in the district heating supply system. We have calculated the energy conservation consequences of a 2-track reform where we have changed to 100% variable tariffs in combination with the introduction of public guaranty that makes 30 years, 2% loans possible. The conclusion is that if this 2-track reform is implemented, the economic incentives for a reduction of heat consumption of around 50% seems to be in place. Without these rather simple reforms it is unlikely that the needed energy conservation goal will be implemented. Danish energy scenarios mostly aim at reducing heat demand from residential houses by around 40% per m2 before 2050. At the same time, the m2 area is supposed to increase, so that the total demand for heat in 2050 is supposed to be just slightly lower in 2050 compared with 2015. This assumed reduction in heat demand per m2 is carried out concurrently with a radical change in the energy supply system towards 100% renewable energy supply. And there are good reasons to believe that a major part of the heat supply system in coming Danish smart energy systems will be wind power in combination with district heating, heat pumps and heat storage. This will be supplemented by geothermal, solar and some biomass heat. In this process of fundamental change of the energy and the district heating supply system, the amount, timing and character of conservation measures at the heat markets become both technically and economically essential, both for the development of smart energy systems and for the 4th generation district heating systems. The main requirements for heat conservation in a smart energy- and a 4th generation district heating system are summarized in table 1. NOT ONLY IN DENMARK The suggested reform has been evaluated in a Danish context with a focus onmultifamily apartment buildings. A similar reform could well have a similar effect in other European countries, and especially the connection between heat conversation, low temperature district heating and the efficiency of renewable energy in connection with heat pump is of general interest.
1. Heat conservation requirements
2. Why these requirements?
a. Right/optimal amount of heat conservation.
a. Optimization between investments in supply and demand systems. Especially relevant in the present strategical change to 100% RE supply systems. b. To avoid investments in oversized supply systems in a situation with not optimized heat consumption. Especially needed in the present situation with a strategical change of the energy supply system. c. To make it possible with existing district heating pipes to supply the needed heat in low temperature systems - and thus avoid new investments in district heating pipes. d. To support a high efficiency/COP of heat pumps in a system with mainly wind power based heat pumps.
b.In right time of heat conservation investment.
c.Heat conservation that supports low temperature systems
Table 1. Energy conservation requirements in a smart energy system
In a future 100% renewable energy based smart energy system, it is mainly an economic optimization between energy supply and energy conservation that determines the optimal level of energy conservation in houses. A bit too simple expressed: If, in a 100% renewable energy based system, it is more cost efficient to heat 100 m2 house area by adding some centimeters to the length of the wind turbine blades than to the thickness of insulation, then this should be done until the marginal costs of prolonging the wind turbine blades (or building one more wind turbine) are equal to the marginal costs of increasing the thickness of insulation. This is a new situation, and calculations in Denmark show that with a 100% CO2 free energy supply system, the optimal heat consumption level is around 80 kWh/m2 heated area for older houses, and 55 kWh/m2 for new houses. In a smart energy system, heat conservation is not only conservation in the heat sector, but heat conservation in a smart energy system. Similar, electricity conservation is not electricity conservation in an electricity sector, but electricity conservation in a smart energy system. So the value of heat conservation is dependent upon the type of supply system, and the level of electricity conservation. The value of electricity conservation is a function of the energy system and the level of heat conservation.
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