Royal Botanic Gardens – Kew

Scope

Air Source Heat pumps & prefab plantroom solution for high profile heritage public buildings/arboretum under PSDS funding

Project Overview

Kew Gardens is a botanic garden founded in 1840 in southwest London that houses the largest and most diverse botanical and mycological collections in the world. It is a World Heritage Site and a top tourist attraction.

Alternative Heat Ltd were appointed to deliver the Jodrell Laboratories and Melon Yard Decarbonisation Project at Kew Gardens. The project includes the provision of a new low temperature hot water (LTHW) heating system using combination air source heat pumps with second stage temperature raising water source heat pumps , with 2No. 595kW duty/standby electric boilers, to serve the Jodrell Building and Melon Yard glass houses. The main works were commissioned in April 2024, followed by the award of additional works to further upgrade the Jodrell Basement plantroom. The contract includes a one year servicing agreement on the main works.

The LTHW heating system is split across 3No. plantrooms: Basement, Modular and Lecture Theatre. Equipment includes:

• Air Source Heat Pump (ASHP):
  • Heating Capacity: 278.7kW
  • Gross COP (per unit): 3.31
  • Flow Rate (m³/h): 61.9
• Water Source Heat Pump (WSHP):
  • Heating Capacity: 803kW
  • Gross COP (per unit): 2.91
  • Flow Rate (m³/h): 64.4
• Electric Boiler
  • Heating Capacity: 595kW

The new 60m² Modular plantroom was designed and prefabricated off site in our manufacturing facility, then transported to and installed on site.

The LTHW heating is distributed from the main modular plantroom via cascaded air-to-water / water-to-water air source heat pumps as part of a 2-stage strategy. The air-to-water heat pumps operate at temperatures of 35^oC/30^oC. The heat produced by the ASHPs is transferred to 8,000L buffer vessels. The water-to-water heat pumps raise this and operate at temperatures of 85^oC/74^oC. The heat produced by the WSHPs is transferred to 2,000L buffer vessels.

The project delivers the following decarbonisation measures and building fabric upgrades:

• New 500 litre unvented hot water cylinder provides hot water to Jodrell Reception and Lecture Theatre. The cylinder comes with hot water return and de-stratification pumps and cold feed expansion set.
• 46 kWp solar photovoltaic array rated at 38,800 kWh per annum installed across the Wolfson Wing and Reception roof to generate electricity to offset the increased demand from the new heating system.
• New high efficiency, Ecodesign for Energy-Related Products Regulations (ErP) compliant, bidirectional supply and extract air handling unit (AHU) which utilises heat recovery and an integral heat pump to provide conditioned fresh air to the Lecture Theatre.
• New 1500kVA unit UK Power Networks (UKPN) low voltage (LV) switchroom located adjacent to the existing substation including all connections (including trenching), new LV panel, replacement of Gent, migration and switchover to the new supply.
• The LV power supply has been provided with resilience in the event of mains power failure via a new 1250kVA generator located adjacent to the modular plantroom.
• New 500kVA generator provides resilience to the Bells generator 6 serving the existing building.
• New Wolfson Wing, Reception and Lecture Theatre roofs and new Lecture Theatre / plantroom facade.
• Jodrell Basement plantroom upgrade works.