COMMISSIONING | HEAT-RECOVERY VENTILATION Heat-recovery performance may not be consistent across the operational range, so it is essential to measure high and low airflow rates at the outset Making the most of free heat There are increasing opportunities to capture waste heat, and its costs can be covered by subscription models, says ICS Cool Energys Dave Palmer W ithin every building and process application be it a hospital, a warehouse, or a chemical plant where there is a cooling system, there is heat produced by the chillers. This energy is available for free, and instead of being rejected to the atmosphere, it can be recovered, harnessed and used. While practically every building and application has a heating need such as domestic hot water this, unfortunately, Thankfully, with the latest innovations, the markets receptiveness to decarbonising heating applications is increasing. Customers are starting to move away from the boilers and are identifying new opportunities. Heat-recovery unit systems should be installed, most effectively, in buildings with an air permeability of 3m3.m-2 hour-1 at 50Pa or lower. Passivhaus Trust implies that the system will recover the same amount of energy, regardless of the amount of air leaking through the building structure. However, uncontrolled entering cold air to the building increases energy consumption to maintain thermal comfort. As a result, the buildings carbon emissions increase. A key element related to the energy efficiency of the ventilation system is the specific fan power (SFP), which defines the power required to move the ventilation air through the ducted system. Typical installations will include MVHR units that can recover 90-95% of the otherwise rejected heat and operate at SFP ranges between 0.50W/l/s and 0.90W/l/s in flats. The number of wet rooms within the dwelling will affect the unit performance. Modern systems are generally designed to operate efficiently; however, ensuring that the installed system SFP is similar to the design expectation is an important element of the commissioning process. The heat-recovery performance may not be consistent across the operational range, so it is essential to measure high and low airflow rates, as well as system pressure while operating. Other commonly encountered issues include blocked filters that are likely to result in poor indoor air quality, impaired ability to provide heat, or increased energy usage because of higher power loads. heat pumps open the door to savings reaching 40% of the energy costs taking the load off the boilers and reducing the reliance on fossil fuel. The combinations are numerous, including: heating while cooling (chillers with heat recovery); heating while cooling or heating (heat pumps with heat Despite a heat pump having lower operational cost, the typical investment with a payback is, for many, not attractive enough compared pandemic, nervousness around capital investments has only increased. However, reaching beyond product innovation, another stimulating factor typically allow building owners and operators to get a bespoke free heating solution installed in their process for a monthly or quarterly fee, which can be exchanged and upgraded as technology improves, or adapted to meet their changing requirements. This is also likely to offer full machine maintenance and warranty cover without the need for capital investment. DAVE PALMER is general manager for UK and Ireland at ICS Cool Energy 72 May 2021 www.cibsejournal.com CIBSE May 21 pp71-72 Heat Recovery.indd 72 23/04/2021 16:15