ulster.ac.uk Heat Pumps and Thermal Storage – Household Implementation to Grid Challenge Professor Neil J Hewitt Director, Centre for Sustainable Technologies

Demand Side Management Heat Pumps & Thermal Storage – an enabling mechanism Heat Pumps Decarbonisation of space heating Markets Technology Challenges Novel Approaches Policy Implications Commercial Possibilities Behavioural Change

Heat Pump Developments Air-source for direct retrofit CALEBRE Economised Vapour Injection Experimental Facilities Compressor/Expander Experimental Facilities ASHP Test Chamber

Heat Pump Developments Air-source for direct retrofit CALEBRE Economised Vapour Injection Lab Results Completed

Heat Pumps i-STUTE WP3.3 has a number of roles for advanced air source heat pumps: Demand side management/response Integration with storage Upgrading Heat Pump New working fluids Meeting householder thermal needs Understanding wider domestic heat demand patterns Integration into energy markets New business models for heat pumps & thermal storage

Heat Pumps Heat Pump, Storage & Control

Heat Pumps Control Strategy 1. DIRECT3. INDIRECT2. STORING

Heat Pumps Control Strategy System Operator Data Online for NI Actual System Demand Forecast System Demand Digital Temperature Sensor on storage tank – Direct connection to RPi 1.Programme gets data from web and tank temp sensor 2.Calculates demand data 3.Makes system mode decision based on forecast demand and tank temperature 4.Activates or deactivates control relays 5.Repeats loop every minute

Heat Pumps Performance

Heat Pumps and Thermal Storage 1. Insulation Improvements Simple Fourier Heat Loss calculation 75mm Spray Foam (0.035 W/mK) =>25% of the stored heat is lost every 24 hours. VIP Insulation (0.007 W/mK) => 4% of the stored heat is lost every 24 hours. HAVE A SQUARE TANK!

Heat Pumps and Thermal Storage 2. Tank Size Reduction Integration of thermochemical store with air- source heat pump Low energy buildings <50 kWh/sq.m/year? Maximum size of store = 2.5 cu.m Energy density for 100 sq.m house = 50 x 100 kWh/year i.e. 18 GJ 2.5 cu.m store leads to an energy density of 7.2 GJ/cu.m being required – This is a major challenge!!!

Heat Pumps and Thermal Storage 2. Tank Size Reduction Trausel et al (2014) – salt hydrates – 3.17 GJ/cu.m – Also is temperature too high? PCM or Sorption? Low temperature salts? Hardorn,JC. Thermal energy storage for solar and low energy buildings – IEA Solar Heating and Cooling, Task 32, 2005.

Heat Pumps and Thermal Storage 2. Tank Size Reduction Low temperature salts – N’Tsoukpoe et al (2014) when including the efficiencies = 120 kWh/cu.m = GJ/cu.m Assumption – 33% EFFICIENCY! UK Domestic Example -40kWh for 3 hours+ DSM -1/3 cu.m? (or insulate house?)

Heat Pumps and Thermal Storage 2. Tank Size Reduction Challenges when using TCM or PCM Fixed operation heating temperature for the heat pump I)No weather compensation II)No reduced running temperatures III)Poor COPh?

Heat Pumps and Thermal Storage 3. Novel Heat Pump & Tank Design 1.Use new working fluids to “allow” store to “lead” 2.New working fluids for high temps.? i)R245fa, R290 ii)R1234yf, R1234ze etc R245fa Under very favourable conditions!

Heat Pumps and Thermal Storage 3. Novel Heat Pump & Tank Design Microencapsulated PCM (High Density Slurry Store) Water + PCM 0-40% Entrainment Pump Circulator Pump Sparger Effect Variation in PCM Slurry = Entrainment Pump and Circulator Pump proportional Operation = desired slurry

Heat Pumps and Thermal Storage Controls & Control Strategies What if? Economy 7 style..

Heat Pumps and Thermal Storage Controls & Control Strategies What if? Market Load Needs type..

Heat Pumps and Thermal Storage Controls & Control Strategies What if? Market Voltage/Frequency Needs.. Impact of electric vehicle charging on residential Distribution networks: an Irish demonstration initiative Richardson et al, 2013

Heat Pumps and Thermal Storage Controls & Control Strategies What if? Market Voltage/Frequency Needs.. On/Off V. Current VSD V. Current Best? The two newly launched variable speed models offer a capacity range from 1 to 10 kW and coupled with Emerson qualified inverter drives allow for a modulation range with speed variation from 15 to 120 Hz

Heat Pumps and Thermal Storage Controls & Control Strategies What if? Low Capacity Heating Needs Heat Genius & Husky Heat Pumps

Heat Pumps and Thermal Storage And the rest………. Need a smart grid? Need to aggregate their performance to avail of Balancing Agreements? Need to address low voltage network stability and its knock- on effects? Can we build in for £200/kW? Can you spare a couple of square meters? Would you like a more tightly controlled home?

Heat Pumps Thermal Stores What type and size of thermal storage system in the future? (when working with an advanced air-source heat pump in a tightly controlled home and responding to market signals???)

Thank you for your attention Questions?