P20
The motivation tariff used in Viborg is a model, where the supply temperature as a yearly average is used to calculate the goal for the return temperature. Both the average supply and return temperature can be collected from the Kamstrup energy meters used in Viborg. Viborg DH Company also works closely with their customers to help them save money, improve comfort and thereby add to the substantial saving for the district heating company. MOTIVATION MODEL – EFFECT FOR THE CUSTOMER The motivation model used in Viborg is straight forward. If you cool the water well, the DH company offers a bonus. If your installation is old and inefficient, you will have to pay extra – a strong incentive to improve your system.
The figure below shows the normal supply temperature at the consumer over a year in different building types. The different heat curves show the supply temperature for comfort heating in different buildings, where the heating system has been dimensioned to different supply temperatures – mainly based on energy efficiency of the building and the radiator system. If it is possible to divide the heat network into separate sections, then it is possible to take advantage of the different demands for supply temperature in the design of the different heat network. Read more of Viborg’s thoughts on their website www.viborg-fjernvarme.dk/nyheder/ny-rapport-fra-niras/
Hours
As is shown in the figure, the demand for domestic hot water (supply temperature at 60°C) will set the temperature demand most of the year. Even with the 90°C-degree heat curve only around 1,800 hours a year, it will require a supply temperature above 60 to provide comfort heating. RETURN TEMPERATURE MUST BE LOWERED In essence, the DH company in Viborg has to deliver a supply temperature of 60°C degrees in more than 7,000 hours every year. Hence, it is of interest to find ways to motive the consumers to lower the return temperature. The return temperature is more or less set by the temperature level of the two heat demands. It is recommended to have a comfort heating in houses at around 21°C. The theoretical return temperature is therefore close to this temperature. Normally, around five degrees higher is possible. So a goal of 25°C from the comfort heating is not impossible to reach. The domestic hot water has a temperature need for circulation at 50°C degrees, so normally the return temperature from this is higher than from comfort heating. If there is no circulation, the domestic hot water can have a return temperature at the same temperature as comfort heating, since the temperature on the cold side is the domestic cold water. THE GOAL IS SAVING MONEY FOR THE CUSTOMERS To be able to motivate the consumers, there must be a goal for them individually. In Denmark, there are different models on how to do that. Some of them are used because the energy meters cannot collect the data needed for a model as described below.
If the return temperature from a consumer is at the calculated level or up to 6° higher, the consumer simply pays the standard price for DH. He is a normal consumer with a normal heat installation that is functioning normally. The customer is within the neutral zone, where he simply pays the standard price. If the consumer can deliver a lower return temperature, there is money to be saved. If the annual average return temperature is below the calculated return temperature, the consumer will get 1 % discount per degree that he is below the calculated return. For some home owners this is an important saving compared to their overall energy bill. The saving can finance improvements in the heating system – and potentially also provide a better comfort in their home. Tip! The saving area has been divided into two areas, where the highest reduction is when the supply temperature is below the promised by the DH company, to remove the customers’ focus from whether the supply temperature is always above what has been promised, and to whether they can actually heat their homes properly and simply be a happy customer, as they save even more.
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