COST MODEL | LARGE-SCALE HEAT PUMPS Cost model Large-scale heat pumps Aecoms cost-management team compares heat pumps to traditional boilers and chillers for low-temperature hot water and chilled water generation in a large, speculative commercial office block development within the M25 W ith an increasing drive from developers to demonstrate their green credentials, and a demand from tenants for more environmentally friendly buildings, the use of heat pumps is on the rise not only as part of the heating/cooling installation, but as a replacement for traditional boilers and chillers. Commercial developments for offices and residential buildings have to compete for tenants, sales and investors, and one way to achieve a commercial edge istodemonstrate how they help to reduce carbon. Legislation is driving interest in the built environment switching from traditional fuel sources to lower-carbon technologies using renewable energy, such as solar, geothermal, tidal, water and wind. Alternative heating and cooling systems are being developed to combat environmental challenges and, as a result, largescale heat pumps are becoming a viable solution. They demand more electricity than traditional boilers and chillers, but the National Grids movement towards a larger proportion of its energy coming from renewable sources such as solar and wind is making large heat pumps farmore attractive, as their lifetime carbon footprint will be reduced. A word of caution over demanding more and more electricity from the Grid, however. In recent years, therehas been a push to make office developments taller and toincrease the density of populations on floor plates, to make projects more economic. From a residential perspective, the growing population requires both low-and high-rise development and, in certain locations, it isincreasingly difficult to deliver electricity at a cost that makes the capital expenditure (capex) of heat pumps viable. Despite the potential for heat pumps to result in higher capital costs, these can be offset over the lifecycle of the equipment because of higher efficiencies. The energy-saving characteristics of heat pumps Example of a heat pump with output ratings up to 1,200kW [Source: Viessmann] make them eligible for the Enhanced Capital Allowance (ECA), so businesses can set 100% of the asset costs against their taxable profits in a single tax year. There is potential to tap into the Renewable Heat Incentive a government environmental programme that gives financial incentives to promote and increase the uptake of heating from renewable sources. It has two schemes non-domestic and domestic which have separate tariffs, joining conditions, rules and application processes. Depending on the scheme, quarterly payments are given over a number of years to eligible installations, based on the amount of heat generated. As with any alternative to traditional approaches there are advantages and disadvantages (see panel opposite). Many of the disadvantages of the heat pump approach can be overcome. The initial high capex cost isoften stated as the primary reason for not considering them. With more units and manufacturers coming to Central plant air-cooled chiller + gas-fired boiler Description Qty Unit Rate Total Heat source Boiler Flue Primary pump set/pressurisation units Primary distribution 1,170 100 1 1 kW m item item 47 640 58,000 87,000 54,990 64,000 58,000 87,000 Chiller 1,450 kW 260 377,000 CHW primary and secondary distribution LTHW secondary distribution 15,000 15,000 m2 m2 22 17 330,000 255,000 15,000 m2 3 45,000 1 item 50,000 50,000 1 item 50,000 Space heating and air treatment Gas installation Gas distribution Electrical installation Mechanical equipment power supply Communications, security and control systems Controls Total costs 50,000 1,370,990 32 July 2019 www.cibsejournal.com CIBSE July19 pp32-33 Cost Model.indd 32 21/06/2019 14:47