Helping Building Services Engineers Apply Low Carbon Technologies

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Leslie Patrick
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1 Helping Building Services Engineers Apply Low Carbon Technologies SAV Systems Scandia House Boundary Road Woking Tel: 0044(0)

2 Focus on OPEX to Achieve Low Carbon 1. Delta T Delta T Delta T 2. Design to Maximum Delta T all seasons 3. Variable Volume 4. Flow temp a Function of Return

3 Delivering 4MWh Delta T 40 / 21,500 Litres Delta T 30 / 28,667 Litres Delta T 20 / 43,00 Litres Delta T 10 / 86,000 Litres

4 How to achieve well functioning low carbon central plant systems Challenge is that most systems are running inefficiently Aim is to lower the return temperature

5 Low Return Under All Load Conditions Design Condition -4 C 70/40 C Shoulder Months 60/40 C Summer 55/40 C

6 Danish Model The adoption of low carbon technologies in Denmark is being driven by the operators of district heating schemes, combined with high carbon taxes.

7 Low returns save money! Less heat lost in the distribution pipework Reduced electricity cost to run pump No need to extend the DH distribution pipe Potential higher electricity production at the CHP plant Less cost for the DH operator Less cost for you the customer

8 Why are low returns important?

9 Management Objective Continuous Monitoring of Return Temperatures and Calculating Delta T Ultrasonic heat meter

10 Distribution Heat Losses Wast

11 Objective Achieving the lowest possible energy consumption and avoiding unnecessary energy wastage! Strategy Follow the Danish experience and focus on system return temperatures.

12 Strategy - Focus on system return temperatures AM12/2013 Combined heat and power for buildings It is recommended that, for new systems, radiator circuit temperatures of 70 C (flow) and 40 C (return) are used with a maximum return temperature of 25 C from instantaneous domestic hot water heat exchangers.

13 Complete System Approach Needed! Supply Side The Central plant Thermal Store Control Pipe & Flow sizing Variable Flow Demand Side Radiator Systems FCUs DHW generation Soft Landings Continues Monitoring

14 Supply Side - Heating Plant Primary energy efficiencies 80/60 C Heat Pump/Condensing Boiler

15 Supply Side Thermal Stores Primary energy efficiencies 80/60 C P = 4.2 Q t Energy storage

Supply Side Thermal Stores AM12/2013 Combined heat and power for buildings A thermal store will only be successful with a variable flow building heating system that can maintain low and constant

16 Supply Side Thermal Stores AM12/2013 Combined heat and power for buildings A thermal store will only be successful with a variable flow building heating system that can maintain low and constant return temperatures, so that the stored energy is maximised litres storage with delta T of 20 deg. (80/60) has capacity of 23 kw litres storage with delta T of 40 deg. (80/40) has capacity of 46 kw.

17 Supply Side CHP AM12/2013 Combined heat and power for buildings Normally, a fixed flow temperature is required from the CHP unit, and the mixing circuit should be used to control the flow temperature off the unit by injecting flow water into the return as required. CHP System

18 Supply Side - District Heating Plant Primary energy efficiencies 70/40C Condensing boiler, Heat Pump

19 Supply Side Central Plant Low Load (20%)

20 Supply Side Central Plant Medium Load (40%)

21 Supply Side Central Plant High Load (100%)

22 Supply Side Flow Rate 80/70 C Q = 3kW K = kg/s 70/40 C Q = 3kW K = kg/s Decreasing Flow Rates Decreasing pipe sizes Decreasing pump sizes Decreasing pump energy Increasing terminal units sizes?

23 Plant Pumping Energy Control pumps at extremities Local Differential Pressure Control Bypasses kept to a minimum

24 Flow Temperature Function of Return

The valve consist of following: (1) The proportional valve / Pilot valve. (2) Thermostatic control valve. (3) Differential pressure controller. (4) Thermostat with sensor.

25 The valve consist of following: (1) The proportional valve / Pilot valve. (2) Thermostatic control valve. (3) Differential pressure controller. (4) Thermostat with sensor. Pressure and Temperature DHW control DH Flow. 70C DH Return. 20C (2) (4) Temp sensor. DHW 50C 10C Cold water supply. (1) Proportional valve. (3) Differential pressure controller.

26 Demand Side DHW

27 System design: units, pipe and central plant

28 Management Objective Continuous Monitoring of Return Temperatures and Calculating Delta T Ultrasonic heat meter

29 Delivering 4MWh Delta T 40 / 21,500 Litres Delta T 30 / 28,667 Litres Delta T 20 / 43,00 Litres Delta T 10 / 86,000 Litres

30 Going forward Lack of design standards Coming at the end of this year Poor understanding of functioning of HIU and its purpose all about the return Lack of product standards Design Issues Diversities Change is needed for central designs with HIUs to continue

Heat networks: Code of Practice for the UK

Heat networks: Code of Practice for the UK Launch: 8 July 2015 18:30 Welcome (Phil Jones, Chair) 18:35 Phil Jones 18:45 Paul Woods 18:55 Tim Rotheray 19:00 David Wagstaff 19:05 Q&A 19:10 Thanks 19:15 Drinks