BESA HIU test procedure. Martin Crane. Carbon Alternatives

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1 BESA HIU test procedure Martin Crane Carbon Alternatives

2 Carbon Alternatives DH technical issues / problem solving Advice on improving specification energypro for detailed economic feasibility of DH DH research 2 x DECC funded projects, IEA research, papers at conferences, contributed to HNCoP. Looking at community ownership options for DH

3 Temperature Typical system return temperatures From block of 150 apartments Flow temperature ( C) Return temperature ( C) Apr 01 Apr 31 Mar 30 Mar 29 Mar 28 Mar 27 Mar 26 Mar 25 Mar 24 Mar 23 Mar

4 The benefits of achieving low return temperature: Low return temperatures = larger dt = lower flow rates (for same kw delivered) = small pumps and pipes Smaller pumps / pumped volume = lower capital costs and lower power consumption Smaller pipes = smaller surface area so lower heat loss Lower return temperature = cooler return pipe = lower heat losses Lower heat losses = less heat input into DH network and reduced unwanted heat gains in buildings Lower return temperatures = potentially improved boiler efficiency, extra CHP heat recovery, improved solar and heat pump performance Larger dt = more thermal storage per unit volume of thermal store = smaller thermal store for same heat storage capacity

5 Factors determining DH return DHW generation Space heating system temperatures DHW / space heating plant operation when no load By-passes on DH network Heat exchangers on the DH network e.g. at building entry

6 HIU performance in practice Data from Guru Systems research project

7 The HIU test Developed as part of a BEIS (DECC at the time) funded research project looking into using AMR data to identify issues on DH networks Test developed from Swedish District Heating Association test Evaluate performance of domestic HIUs during: space heating (indirect), DHW generation (instantaneous), standby To explore / demonstrate impacts of different design specification Range of DHW and space heating temperatures Maximum DHW outputs and DHW delivery time after standby period Use of VWART volume weighted average return temperature as the key performance metric.

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10 Substation performance metric The volume weighted average return temperature (VWART) was calculated for each substation function, DHW, space heating and standby Single VWART figure calculated based on typical DHW (1420 kwh /year) and space heating demands (1450 kwh/year) and standby operation at other times Real consumption data has been used make the patterns and magnitudes of demands similar to real, measured, customer demands Both the DHW 6, 10 and 13 l/minute) and space heating loads 1,2 and 4kW) used in VWART calculation are much lower than the peak substation output. Overall VWART is single figure indication of a substation s annual performance

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12 VWART results

13 VWART results

14 Results annual primary flow

15 DHW supply

16 Standby operation 2nd International Conference on Smart Energy Systems and 4th Generation District Heating, Aalborg, September 2016

17 How to use the test 1. Specify a VWART 2. Use test data in design 3. Tweak it if your site has different heat loads 4. Use the test VWARTs as acceptance criteria 1. At HIU 2. At Energy Centre 5. Do your own test to estimate impacts of changes

18 1. Specify VWART Overall or separate VWART elements With or without keepwarm? Are you system temperatures the same as the Test? Probably OK if not. Other things the test could allow you to specify: HIU heat loss at standby DHW response time

19 2. Test data in design Pipe sizing dt DH dt during highest DHW delivery DH dt during highest space heat delivery Pump sizing Standby flow dictates required turndown of pumps Heat loss calcs Base on VWART for return and consider use of standby flow temperature?

20 2. Test data in design pipe dt From this data the pipe sizing temperature difference can be set. DHW up to 50C dt Space heat up to 30C dt

21 2. Test data in design - Standby Pumps must operate OK at this flow rate This temperature sets the heat loss on the DH return pipe

22 3. Tweak eg higher space heat The standard VWART calculation based on new build flats but what if old stock / larger? Change the VWART calculation.

23 3. Tweak different DHW Again could change the VWART calculation for different DHW demands

24 4. Commissioning / acceptance criteria Use energy centre heat meter to check performance eg: Return temperature at 3am, difference in/out of space heating season. Turn all the heating on and check return temperature (or just do a floor and monitor temperature there) Actual VWART up to end of defects period Individual checks of HIUs at commissioning. Don t accept phasing issues as cause of high return temperatures

25 5. On-site VWART estimate Can do on site using HIU heat meter. Set DH flow temperature run the DHW at test outputs, Run space heat at test outputs May need to balance radiators to get 40C return temperature on secondary will need to measure secondary return temperatures. Need to allow time for system to stabilise. Without accurate balance will get idea of dt between radiator and secondary return. Standby more challenging Can asses standby flow rate and heat losses (record heat meter m3 and kwh ) over say a week. More difficult to assess return temp (don t calculate from m3 and kwh as you don t know the DH flow temp at HIU) Some heat meters measure average return temperatures Assess where current HIU issues are? What could be changed and what would be the impacts eg compare with same kit in tested HIU.

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27 VWART Volume DHW Standby Space Heating Period VWART % Time No Heating % Heating % Overall 51.7 DHW Draw test results Post DHW Draw (60 seconds) Power (W) Primary flow (m3/hr) Return Temp( C) Primary flow (m3/hr) Avg Return Temp( C) Low Medium High Standy test results Primary flow (m3/hr) Return Temp( C) Standby HIU test gave 54C VWAR Space Heating test results Power (W) Primary flow (m3/hr) Return Temp( C) 1kWp kWp kWp

28 The Test going forward BESA steering group open to ideas 2 UK test houses setting up to be able to run the test Current test information Only a single HIU so far Old test version results of 6 HIUs tested and VWART calculation method at

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