The key benefits of second-generation heat pumps using propane (R290) for district heating networks include:

1. Reduced carbon footprint: By using a natural refrigerant with a very low global warming potential (GWP of 3), propane heat pumps significantly reduce the environmental impact compared to synthetic refrigerants.

2. High-grade heat: Propane can achieve high flow temperatures of up to 70°C, making these heat pumps ideal for a variety of heating applications and for optimising thermal storage use.

3. Improved efficiency: Propane heat pumps are sensitive to return temperatures, and as the return temperature decreases, the delta T increases, leading to improved SCOP (Seasonal Coefficient of Performance). This directly reduces electricity consumption, operating costs, and carbon footprint.

4. Alignment with hydronic heating systems: Second-generation heat pumps are designed for heating-first operation, using high delta T and variable flow to align with the requirements of real-world hydronic heating systems, rather than forcing the systems to adapt to cooling-led equipment.

5. Role in heat decarbonisation: As heat pumps are a key part of the UK's heat decarbonisation strategy, the careful selection of high-performing, sustainable heat pump technologies like propane is essential to ensure optimal building performance and support the transition to a low-carbon future.

The DELTA series of modular heat pumps offers the following typical configurations and key specifications:

1. DELTA-HP1: Monobloc air source heat pump with a maximum capacity of 115 kW, a capacity of 90 kW at -5°C ambient, and a nominal COP of 3.67 at 7°C ambient and 45/30°C water temperatures.

2. DELTA-HP2: Monobloc air source heat pump with a maximum capacity of 207 kW, a capacity of 177 kW at -5°C ambient, and a nominal COP of 3.87 at 7°C ambient and 45/30°C water temperatures.

3. DELTA-HP3: Monobloc air source heat pump with a maximum capacity of 341 kW, a capacity of 265 kW at -5°C ambient, and a nominal COP of 3.95 at 7°C ambient and 45/30°C water temperatures.

4. DELTA-HP4: Monobloc air source heat pump with a maximum capacity of 418 kW, a capacity of 351 kW at -5°C ambient, and a nominal COP of 3.99 at 7°C ambient and 45/30°C water temperatures.

All DELTA series heat pumps use propane (R290) as the refrigerant, which has a very low global warming potential (GWP of 3), and are designed for commercial building and district heating network applications, providing heating and domestic hot water.

In a hybrid energy centre, second-generation heat pumps are integrated in the following way for optimised performance:

1. Sizing: Heat pumps are sized to provide the maximum share of energy (kWh) rather than being sized to the peak building load (kW). This is a more cost-effective approach, as sizing heat pumps to the peak load would result in over-sized and under-utilised appliances.

2. Peak capacity: The cost-effective peak capacity is provided by boilers, which complement the heat pump operation and ensure the overall heating demands are met.

3. Vapour refrigeration cycle: Heat pumps use a vapour refrigeration cycle to generate hot water by harvesting energy from a lower temperature source, such as air, water, or other sources. The input energy is electricity to power the compressors and fans.

4. Efficiency: The efficiency of the heat pump system is measured by the Coefficient of Performance (COP), which is the ratio of heat output to electricity input. Seasonal performance is also important, as it considers the overall efficiency over the course of the heating season.

5. Optimised operation: By sizing heat pumps for maximum energy (kWh) contribution and using boilers for peak capacity, the hybrid energy centre can operate in an optimised manner, providing cost-effective and energy-efficient heating solutions.