02 May 2012 06:05:50
Ecovision uses leading edge renewable energy design and technology at The Daresbury Science and Innovation Centre
The Daresbury Science and Innovation Centre is an innovative project that uses leading edge renewable energy design and technology to deliver both heating and cooling whilst minimizing any impact on the environment.
The brief from Vinci Plc, was to design and install a renewable energy heating and cooling system that integrated with other elements of the building to achieve a BREEAM “excellent” rating. The installation combines the natural resource of the huge aquifer on which the site sits with minimal mechanical support (pumps. A world class water source heat pump installation to deliver a shining example of design excellence with minimal environmental impact. This exemplary installation has peak pumping rates of up to 30 litres of water per second. Other significant features of the system are highlighted in bold.
Contribution to environmental issues and summary of key facts why installation/concept is sustainable:
• no fossil fuels like natural gas or oil are being used in the building
• minimize the CO2 emissions for heating and cooling the building
• taking advantage of the fact that the site lies over one of the largest aquifers in the UK
• uses the “free latent energy” in the ground water for heating and cooling the building
• smart controls minimize the energy consumption of the secondary circulation pumps and the well pump by using inverter drives, which adapt to the demand in the building
• using a “concrete core activation” system, thus maximizing the heating/cooling emitter surface-area, allowing “free cooling” and the most efficient operation possible of the heat pumps
Ecovision designed and installed a renewable energy system to enable the Centre to benefit from the huge aquifer on which it sits and to reach the sustainability targets of the North West Development Agency, as well as achieving BREEAM Excellence. The Permo-Triassic sandstone forms the second most important aquifer in the UK and provides ground water for public supply, industrial users, agriculture and leisure activities. The Centre itself delivers world-renowned science and innovation and so Ecovision’s renewable energy installation was needed to reinforce the excellence and sustainability of the work the centre produces.
Ecovision carried out a feasibility study involving hydrologists to establish the possibility of installing a Water Source Heat Pump with open loops to heat and cool.
Borehole records were obtained from the British Geological Survey and information on licensed groundwater abstractions obtained from the Environment Agency. This information was used to assess the feasibility of an open loop heat pump system. From the proposed heating/cooling loads the required borehole pumping rates were calculated. The potential change in future client requirements was factored in. Peak pumping rates of up to 30l per second were predicted with an annual abstraction rate of 305,000m3.
Ecovision drilled and tested two wells, the abstraction well was drilled to a depth of 120m. This allowed a comprehensive pump-test and established that a flow rate of 30 l/s could be achieved. The abstraction rate peaked at 30 l/s, which is the requirement to cover the full heating and cooling load of the building. Following the successful drilling and testing of the injection wells Ecovision then collated and analysed the data enabling the design team to model the final system design which concluded that there was a requirement for two more injection wells.
The principal of the open loop system is: Groundwater from 65m deep is drawn out via a 15” diameter abstraction well and is passed through a heat exchanger before being re-injected via a series of three 120-150m deep injection wells each of 6-10” diameter.
The abstraction well consists of a 250mm well-liner and stabilizing coarse gravel pack around it. The gravel pack avoids the washing out of the well. Within the well-liner the submersible pump is attached to the riser pipework. The well liner has a slotted section below the well-pump through which the groundwater enters the liner and then the pump.
The injection wells are cased to 30m in depth to prevent injection of water into near-surface formations, removing the potential issue of groundwater flooding into service channels and basements. The casing avoids washing out the injection-well when the water enters under pressure.
The submersible well pump is connected to an inverter drive. The speed of the pump is determined according to the weather-conditions and the resulting heating and cooling demand of the building. Thus avoiding any unnecessary power consumption of the well pump and improving the overall system efficiency.
An integral part of the design of the building is the use of a Velta chilled beam cooling and heating system; this is the most efficient way of cooling large commercial buildings and removes the need for large and expensive air conditioning installations. The chilled beams use the water from the aquifer to cool the building when required. The water is drawn from the ground and passed through heat exchangers where the heat from the building is passed to the cool water from the aquifer, which is then returned to the ground. The only energy required, is used to run the circulation pumps. A chilled water flow temperature of just 18c is enough to cool the building at any time. Thus a chiller is not required to lower the chilled water flow temperature any further
During the heating phase this process is reversed and the heat from the underground water is used by the heat pumps to provide the heating and hot water required by the building during the winter months.
A 300kW heat pump system was installed to meet the buildings heating and hot water loads. Two 130kW low temperature heat pumps are used for heating only. The maximum required temperature is 50c. The heating system consists of a variable temperature circuit for the Velta ‘concrete core activation’ system and fixed temperature circuit for the airhandling units.
One 40kW high temperature heat pump is part of the system. This heat pump can achieve a flow temperature of 70c, which can generate all the hot water to 65c.
The average temperature of the water from the aquifer is approximately 10-12c which means that the heat pump is operating at a much higher efficiency throughout the heating season. A COP of 4.2 is possible over the year for the heating.