ON THE ROAD
Passive behaviour
BuroHappold Engineering’s NewMass cooling solution won an award at the Chartered Institution of Building Services Engineers (CIBSE) annual Building Performance Awards. We look at how its NewMass product passively absorbs heat from a space.
B
uroHappold Engineering has won the Energy Effi cient Product or Innovation category of this year’s Building
Performance Awards with a cooling solution for buildings using phase change materials (PCMs) to passively absorb excess heat from a space. Called NewMass, the new product has been trialled in a primary school where it delivered energy savings of 36% when compared to more traditional chilled beam systems. NewMass impressed the judges at this year’s CIBSE Building Performance Awards which aim to highlight and encourage innovation that leads to improved building performance.
The product was developed by Gideon Susman, an Associate at BuroHappold, as part of his Engineering Doctorate in Environmental Technology. He says it was developed in response to defi ciencies in current passive and active PCM cooling solutions.
The new modular product has been designed to be installed below the ceiling of an occupied space. It comprises a fi nned aluminium tube to maximise its surface area, to help increase the rate of heat absorption or promote natural convection, depending on the mode in which it is operating. The tube is fi lled with a non-toxic PCM with very low fl ammability and combustibility properties.
PCMs are substances that absorb and release thermal energy as they are transformed from solid to liquid and back again. The PCM used in NewMass is based on a salt water mix with additives, designed to change phase form solid to liquid at a temperature of about 21°C. During the day, the solid PCM will passively absorb excess heat from the space, turning the PCM from solid to liquid.
At night the absorbed heat is either passively discharged to the cool night air to enable the PCM to return its solid state. Alternatively, heat can be
22 April 2018
rejected to a chilled water loop which, depending on external conditions, can either reject heat using ‘free cooling’ or reject heat with mechanical cooling using a chiller.
The NewMass modules can also operate in heating mode when supplied with hot water from a boiler or heat pump, which can save money by eliminating the need for radiators or other heat emitters.
To test the eff ectiveness of the design, a prototype was built and trialled at Brunel University in a custom-built test chamber. The tests showed the product compared well against commercially available PCM products, such as wall boards and ceiling tiles with embedded PCMs.
They also showed the prototype was eff ective at moderating the temperature when operating in passive mode and that the unit off ered excellent temperature control during active operation. The system maximises energy savings by prioritising passive cooling operation. Computer modelling predicted the system would save 34% energy for a typical UK offi ce building. The product’s active cooling function ensures the cooling set points are always maintained. Following analysis of the prototype, BuroHappold partnered with ICE Architects to install the system at Brentfi eld Primary School, Brent, north-west London, to see how it would perform in a fully operational school. The trial showed that the system off ered an energy saving of 36% when compared to a passive chilled beam system, an even better performance than the modelling had predicted. As well as off ering energy savings, the installation demonstrated that NewMass can provide comparative or even improved thermal comfort when compared to existing passive systems by subjecting each to the same heating and cooling cycle.
The installation also demonstrated that the product was eff ective in providing heat in heating mode. The product’s low fl ow temperature means that a heat pump may be used to avoid the need for gas-fi red boilers. In fact, in both heating and cooling mode the units are relying on electricity to supply energy when required, will allow the unit to operate on 100% renewable electricity if required.
A further benefi t of the thermal storage is that the system could be adapted for a demand response scenario by allowing the PCM to be charged when the chillers can be run using excess renewable energy and conversely when grid power is in high demand, temporarily halting the active cooling mode to enable the PCM to absorb some or all of the load.
A control algorithm has been developed to control the units based on room air temperature, relative humidity and the phase of the PCM. This will allow the units to absorb maximum possible heat passively before the chilled water loop engages,
Because they are modular the units can be easily relocated. And, at the end of their life, the materials used in the units can easily be recycled. And because the NewMass uses no moving parts maintenance is greatly reduced.
“The NewMass system is an exciting innovation in hybrid cooling systems,” says Mark Dowson, building performance group leader, BuroHappold Engineering. “As climate change becomes more prevalent it’s important we invest now in more resilient low energy solutions to maximise well- being and productivity in environments such as our schools and offi ces. Phase change materials are a highly adaptable and largely untapped source of free cooling in buildings that can be applied in a wide variety of applications – we have only scratched the surface with their potential!”
www.acr-news.com
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