Uncertainties in energy and economic performance of HVAC systems and energy recovery ventilators due to uncertainties in building and HVAC parameters

Energy recovery ventilators (ERVs) are exhaust air energy recovery devices for outdoor ventilation air preconditioning in building HVAC systems. The energy and economic performance of an ERV depends on its effectiveness, cost, maintenance as well as other parameters such as climate, building design and HVAC system parameters. In this study, a sensitivity analysis is used to evaluate the impact of uncertainty of building and HVAC system parameters on the energy savings potential and economics of ERVs. Firstly, the impact of building parameters on HVAC system peak loads, capital cost, annual energy use and operating cost are investigated for an office building located in Chicago using TRNSYS simulations. The results show that the ventilation rate has the most significant impact on total HVAC system energy performance. Secondly, energy and economic analysis on the ERV’s payback period is conducted with a specified variation of each input parameter. The results illustrate that an ERV with 75% sensible and 60% latent effectiveness can reduce the peak heating load by 30%, the peak cooling load by 18%, the annual heating energy usage by 40% and the annual cooling energy usage by 8%, with a payback period of 2 years. The uncertainty of ERV’s payback period to its initial cost, recovery effectiveness, energy rate, HVAC equipment initial cost and efficiency as well as ventilation rate are also presented. A ±25% uncertainty in the 7 building and HVAC system input parameters studied results in a maximum 17% and 225% uncertainty in the payback period of the ERV respectively.