House Installations, district heating substations

Transcription

1 House Installations, district heating substations Energy sources Heat production Distribution Consumer installations End consumption Placed at the end user Purpose of preparing domestic hot water and delivering heat for the space heating Each building is supplied from a branch pipe connecting the building to the overall distribution network

2 House Installations, district heating substations Purpose Cooling of the district heating from consumers Reflects the efficiency of the total district heating system Adjustment To achieve the desirable level of cooling the domestic substations at the consumers need to be correctly adjusted Recommended to have a service made on the installation about every two years Temperature levels In Denmark: Dimensioned for a room temperature around 20 ᵒC, (at outside temperature of 12 ᵒC and a flow temperature from the plant of 70 ᵒC. Other countries have higher temperatures (about 90 ᵒC or higher). The DH flow temperatures have an influence on the considerations that should be taken before the selection of domestic installations

3 House Installations, District Heating substations

4 House Installations, Types of DH substations Stages Direct/ Indirect One stage Two stage Direct coupling Indirect coupling

5 House Installations, Types of DH substations, stages Onestage Simple and compact; relatively low installation cost, fewer parts that can break due to its simple structure Disadvantage: Limited capability to cool the DH water Two stage Two heat exchangers is typically used in large installations where there is a higher consumption of domestic hot water Possible to achieve a lower return temperature than with a one stage installation, during the periods where there is a consumption of hot tap water. Increased capital costs, as well as more mechanical components that can be break

6 House Installations, Types of heat installations Radiators and floor heating Direct coupling Indirect coupling By a direct coupling in the heating installation, the temperature loss through the heat exchanger is avoided, as the district heating water of the system flows directly into the heating installation. An indirect coupling at the consumers give the district heating supplier the opportunity to make larger pressure variations in the network, as the district heating supplier is not constrained by the consumer installations. This is an advantage in greater transmission and distribution networks, where the consumers located farthest from the district heating supplier during peak situations, can have difficulties to maintain the desirable flow temperature, if the pressure in the district heating network is too low A disadvantage of the use of a direct coupling of the heating installation is that if there is leakage from the heat installation, large amounts of water can be emptied from the installation. In Denmark, there is a requirement that new consumer installations must be established with a weather compensation device (reduces the flow temperature in the heating system in relation to the outside temperature). In a directly coupled heating installation, this will result in an increased cost for a circulation pump and a check valve. Requires higher flow temperatures, resulting in higher heat loss

7 House Installations, Types of DH substations Principle of a direct coupling in a domestic heat installation

8 House Installations, Types of DH substations Principle of an indirect coupling in a domestic heat installation

9 House Installations, Adjustment of DH substations Differential pressure regulator The task of this device is to ensure that the valves in the substation is able to control, but also to restrict flow through the substation and thus achieving a better cooling Bypass A bypass immediately after the main taps inside the house installation aims to secure a small but steady flow through the service line whereby this is maintained warm Booster pump Weather compensation Maintains a comfortable flow of district heating water through the house installation. A booster pump is not a standard installation, purpose is to maintain the pressure to the farthest consumers in the network (not often applied) Increases the efficiency of a district heating network, by lowering the supply temperature. There are two types of weather compensation, being at the system level (in the network) and at the consumer level (in domestic installations)

10 House Installations, domestic hot water Tank Dictrict heating flow is relatively low, hence it requires a smaller service line to the consumer. Max 8 kw. A hot water tank will have a heat loss Heat exchanger District heating flow is relatively high since the heat exchanger is placed before the differential pressure controller. Minimum 25 kw. If all consumers in a district heating system have installed a heat exchanger, this will require large power requirements during periods of high hot water consumption

11 House Installations, metering Why measure heat consumption? How to measure generations Flow Energy (flow and temperatures) Basis for tariffs Motivational tariff what is that? (Example from Esbjerg) Smart energy Common with other utility services; water and electricity

12 House Installations, metering

13 House Installations, metering To measure is to know! Daily variations in district heating systems are low The district heating network has both less daily and seasonal heat load variations than the aggregated heat loads of the customers Only about 5 % of the heat is above the daily average heat load in annual basis Daily variations are to a large extend social heat loads Geographical diversity Heat load patterns in customer categories No standard heat load patterns Large variations in heat load patterns among different customer categories To measure is to know!, Henrik Gadd, 2012, Licentiate Dissertation, Lund University, Sweden

14 House Installations, legionella Legionella is a problem that is seen in relation to most types of water systems. Also installations in regard to district heating are at risk. Temperature is an important condition for the survival of the legionella bacterium. The bacteria can survive for months at low temperatures, but die within 5 6 hours at 55 C and more rapidly at higher temperatures. Normally, there is no occurrence of legionella bacteria in domestic installations that are properly balanced, and in which there is a continuous replacement of domestic water. Proper design of the domestic hot water installations There are several techniques for purifying water systems where there has occurred legionella growth, and to prevent legionella growth as for instance electrical heating and chloride treatment. The easiest way for the consumer to prevent legionella is to ensure a constant flow of the water in the domestic installations

15 House Installations, advice to consumers Some of the most common advice to efficient district heating is: Check cooling/return temperature (minimum 30 C as an average over the year) Lower the room temperature (if the temperature is reduced 1 C saves 5 10 % energy) Keep an eye on the radiators the bottom of the radiator should be cold (flow through should not be too high) Use all radiators in a room (for better cooling) Be sure to ventilate and close windows

16 House Installations, prices, single family house

17 House Installations, prices, large building

18 House Installations, prices Investment DKK prices EUR Transmission lines: Transmissionline (not in asphalt) DN100 DN DKK/m EUR/m Transmissionline along road DKK/m 470 EUR/m Transmissionline in road DKK/m 550 EUR/m Note: Investments in transmission lines depends on road works, contractor, pipe supplier, etc. Distribution network: High connectivity >50 % of buildings in area DKK/building EUR/building Low connectivity <50 % of buildings in area DKK/building EUR/building Note: investments in distribution networks depends on building density, road works, pipe supplier, contractor e Connection of apartment complexes will require a larger service line, but the expenses for excavation work will be more or less the same prise per meter. House installations: House installation DKK/building EUR/building House installation, apartment complex 50 kw DKK/building EUR/complex Note: Price include dismantling of old installation For apartment complexes with higher capacity requiment, the investment will be larger.

19 , prices Prices of transmission network Inner DN diameter [mm] Capacity [kw] EUR/m Twin pipe Single pipe