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These utilise the heat from a CHP unit to generate chilled water by using an absorption chiller when cooling is required.

Case Study - Gas Networks Ireland, n.d. Rochestown Park Hotel case study. Available at: https://www.gasnetworks.ie/docs/business/gas-benefits/Rochestown-Park-Hotel-Case-Study.pdf

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These are generally smaller in physical size and heat output than conventional boilers. Multiple modular boilers are usually coupled together to make up the total required duty allowing the boilers to fire separately giving greater flexibility and efficient performance. Other benefits include ease of installation, lower capital costs, reduced standby capacity requirement and space saving.

Case Study - Eurogas, n.d. Upgrade to Mount Anville Girls' Secondary School heating system. Available at: https://eurogas.ie/case-studyupgrade-to-mount-anville-girls-secondary-school-heating-system/

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These use external ambient air as a heat absorption/rejection medium for the heat pump. They are cheaper and easier to install than some other heat pump systems but are subject to outside air temperature fluctuations and are vulnerable to possible physical damage.

Case Study - Public Policy, 2023. Heat pumps and energy retrofit. Available at: https://publicpolicy.ie/downloads/papers/2023/Heat_Pumps_and_Energy_Retrofit.pdf

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These use the ground as a heat absorption/rejection medium for the heat pump. Below ground temperatures are stable throughout the year so offer better efficiency than ASHPs. The disadvantages are the higher capital costs, the requirement for drilling boreholes for pipework and ground make-up on site.

Case Study - Galway-Mayo Institute of Technology, n.d. Ciset case study: HP IRL project. Available at: https://www.gmit.ie/sites/default/files/media/legacy/ciset-case-study-hp-irl-project.pdf

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Case Study - John Thompson, 2019. Case study: 150 TH three-pass bagasse/coal fired boiler. Available at: https://www.johnthompson.co.za/wp-content/uploads/2020/09/case-study-11-150-th-three-pass-bagasse-coal-fired-boiler-jul19.pdf

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These can accommodate two fuels types, such as gas and oil.

Case Study - Cochran, n.d. Foresterhill case study. Available at: https://cochran.co.uk/Downloads/Foresterhill-Case-Study.pdf [Accessed 16 October 2024].

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Condensing increases boiler efficiencies by removing heat energy usually wasted in the exhaust. Removing this energy causes the flue gases to condense resulting in water as a waste by-product.

Case Study -

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Combined heat and power (CHP)/ cogeneration

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Combined heat and power (CHP)/ cogeneration

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CHP units are effectively engines which convert the mechanical energy into electricity via a generator. The 'waste' heat produced by the engine is also utilised for heating and/or hot water, therefore increasing the energy utilised and efficiency of the system.

Case Study - Gas Networks Ireland, n.d. St. Monica’s Nursing Home. Available at: https://www.gasnetworks.ie/business/get-connected/small-medium-enterprises/st-monicas-nursing-home/

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Combined heat and power (CHP). cogeneration

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These operate at atmospheric conditions without a fan or pressurisation and are one single unit. The air/fuel mix is controlled by gas flow drawing the air for combustion. Generally, atmospheric boilers will operate in either 'on/off' or 'high/low' settings and cannot modulate.

Case Study - Zhang, Y., Wang, Y., Li, Y., Liu, J., & Xu, L., 2017. A review on the application of energy recovery technologies in industrial processes. Resources, Conservation and Recycling, 123, pp. 56-67. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0013935117302359

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Using a vapour compression cycle, a heat pump effectively takes ambient heat and converts it to a higher and more useful temperature. Heat pumps can be reversible to also provide cooling.

Case Study - Cambridge City Council, Property Type: 1980s, 6-bed detached, 280 m2 floor area, timber framed with cavity wall extensions.

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Whereas a conventional chiller uses a compressor to raise the pressure (and temperature) of refrigerant in the refrigeration cycle, an absorption chiller uses heat (typically from a CHP system).

Case Study - Birmingham's new landmark library, Centenary Square, Birmingham.

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A fan blows air across a heat exchanger coil that will contain hot or cold water (or refrigerant for VRF/VRV systems).

Case study - Zhang, Y., Wang, Y., Li, Y., Liu, J., & Xu, L., 2017. A review on the application of energy recovery technologies in industrial processes. Resources, Conservation and Recycling, 123, pp. 56-67. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0013935117302359

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Active chilled beams operate in the same principle as the passive with the exception of having fresh air ducted to it. Rather than air being drawn into the beam by buoyancy it is induced by the ducted air.

Case Study - Entropic, n.d. St Vincent’s Hospital chilled beams case study. Available at: https://entropic.ie/case-study/st-vincents-hospital-chilled-beams/

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Regulating dampers direct the air flow to either the heating or the cooling exchanger coil.

Case Study - Amin, A., Kumar, S., & Ranjan, R., 2023. Assessment of energy and economic performance of district heating systems: A case study. Applied Energy, 352, p. 127005. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0959652623041094

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Chilled water is produced via a centralised plant and then circulated to services throughout the building.

Case Study - The Kings Yard energy centre, London Olympic Village 2012.

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A cooling tower is more efficient than a dry air cooler because it uses evaporated water to assist the rejection of unwanted heat but requires greater maintenance.

Case Study - Pearson, A (2015)' A Flying Start' CIBSE Journal

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Warm water is piped across fans within the dry air coolers

forcing the temperature of the water to drop.

Case Study - The London Aquatics Centre for the 2012 Olympics.

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Flat Bedded Dry Cooler - 3D Product Animation

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Long rectangular units located at high level circulate chilled water in finned pipes and exchange coolth. Convection occurs with warm rising air being cooled by the chilled beams.

Case Study - Macquarie Group, Fifty Martin Place in the heart of Sydney's financial district.

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The flow rates of the hot or chilled water in the coils are modulated via control valves to deliver the heating or cooling loads required.

Case study - Iveagh Garden Hotel, Dublin.

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AHUs maintain adequate ventilation by providing fresh, filtered outside air and delivering it at the condition required to the internal space. AHUs can be used to control the temperature and humidity of the air.

Case Study - The new Mary Rose Museum in Portsmouth Historic Dockyard.

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Air is supplied from the AHU at a constant temperature to a number of VAV units, each with a damper which controls the flow of air through it depending on the cooling or heating loads.

Case study - Turnbull & Scott, n.d. Water savings: Dry air cooler case study. Available at: https://www.turnbull-scott.co.uk/case-study/water-savings-dry-air-cooler-case-study/har .

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The system is split into an outdoor heat rejection unit and an indoor room cooling unit. The refrigerant is pumped directly between the units and operates with 2-pipe connections.

Case Study - Hyde Heating and Cooling. (n.d.) Case study: Arthur’s Seat split system installations in a residential home. Available at: https://hydeheatingandcooling.com.au/blog/case-study-arthurs-seat-split-system-installations-residential-home/

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Variable Refrigerant Flow (VRF) and Variable Refrigeration Volume (VRV) systems circulate refrigerant like a split system but have multiple indoor units providing simultaneous heating and cooling. They can operate with a 2- or 3-pipe connection.

Case Study - GTI Energy. (2019) Case study: Variable refrigerant flow (VRF) heat pump systems in cold climates. Available at: https://www.gti.energy/wp-content/uploads/2020/11/Case-Study-Variable-Refrigerant-Flow-VRF-Heat-Pump-Systems-in-Cold-Climates-2019Dec15.pdf .

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FCUs that use refrigerant will often have 3-pipe connections (hot and cold flow and a single return) allowing for simultaneous heating and cooling to separate zones. Some systems achieve simultaneous heating and cooling with only 2-pipes (flow and return) where the flow pipe contains refrigerant in both vapour (for heating) and liquid (for cooling) form.

Case Study -

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2-pipe FCUs have only one coil so they can only provide heating or cooling at any one time. Their mode can be changed on a seasonal basis as required.

Case Study - CIBSE Journal. (2016) Fan module. Available at: https://www.cibsejournal.com/cpd/modules/2016-10-fan/

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4-pipe FCUs have dedicated coils for heating and cooling and thus four pipe connections (hot and cold flow and returns).

Case Study - Facilities where a four-pipe fan coil unit system should be strongly considered would include these characteristics:

• Larger facilities such as college campuses, large residential complexes, large hotels, military facilities where use of chilled water cooling is life cycle cost effective.

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Plant equipment to produce chilled water. Heat is removed from an unwanted area and rejected externally. Packaged chillers include heat rejection as part of the unit. Other chillers require dedicated heat rejection plants, such as dry air coolers and cooling towers.

Case Study - International Commerce Centre (ICC), Hong Kong

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These systems deliver a constant volume of conditioned air from the AHU. They are not suited to multi-zoned buildings with varying cooling requirements, therefore they are generally used in single zones, such as a central foyer or as part of a cooling system with the primary cooling being achieved by other means, such as FCUs.

Case Study - CIBSE Journal. (n.d.) Case study: Going electric at the Electricity Supply Board HQ in Dublin. Available at: https://www.cibsejournal.com/case-studies/case-study-going-electric-at-the-electricity-supply-board-hq-in-dublin/

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These are considered a low-carbon alternative to conventional fuel boiler as it is fuelled by biomass (wood) or biodiesel. The variety of fuels and their respective calorific value can give varying outputs.

Case Study - Westborough Academy, in Essex.