ASHRAE Journal - December 2012 - 44

2012 Technology Award Case Studies
Outdoor Swimming Pool Water Heating
350,000

The 3,360 ft2 (310 m2) outdoor swimming pool is used from mid-May to the end of September. It was 2007 Energy Consumption 300,000 2009 Energy Consumption heated by a 36 kW water heater to maintain a setpoint of 84°F (29°C). One of the new measures consisted of 250,000 two 4.5 ton (16 kW) heat pumps installed in the inte200,000 rior parking. They take air from the garages and exhaust it outside. Their evaporator cools this exhaust air and 150,000 the heat rejected in their condensers is used to heat the swimming pool water. 100,000 A new plate heat exchanger was installed on the pool loop upstream of the existing electric heater where it 50,000 heats the pool water with hot water discharged from the heat pumps. These heat pumps are able to satisfy 95% 0 of the outdoor swimming pool heating load, resulting in Jan. Feb. Mar. Apr. May Jun. July Aug. Sept. Oct. Nov. Dec. energy savings of 83,000 kWh. This measure also imFigure 1: Energy consumption before and after energy retroﬁt. proves the parking garage air quality since it increases the exhaust airﬂow. All the indoor parking controls and ventilation systems were linked to the new building automa- fans, frequency drives and heat pumps are operated from this tion system. This resulted in the implementation of a control new BAS, which facilitates troubleshooting and operation. sequence designed to favor a better air sweep of the garages, This BAS has a web platform, which allows the engineers to reducing CO pockets and levels. follow the operation remotely from their ofﬁces. For the project’s commissioning process, the project engineer Project Summary monitored the systems and automation sequences for a year, The most innovative aspect of this energy retroﬁt project making adjustments and optimizing the operation to maximize was the maximization of heat recovery on exhaust air. The energy efﬁciency. The building operators were involved in the use of heat pumps on the exhaust air allowed cooling the dis- process all along and trained by the engineer to operate the syscharged air at very low temperatures all year-round, ensuring tems efﬁciently. This process was a major factor in the project’s maximum heat recovery and, therefore, rejection in the incom- success and the building owners’ satisfaction. ing outdoor airﬂow as well as elimination of reheat by elecEvery energy-efﬁciency measure within this project resulttric heaters. Furthermore, by cooling the exhaust air at these ed in a signiﬁcant reduction of the electricity consumption and low temperatures, it allows the recovery of latent energy by demand of the public spaces. A total of 1,190,162 kWh was condensing the humidity present in the airﬂow, which was not saved by the measures implemented in this project, representpossible with the heat pipe alone. ing 43% of the total original energy consumption (Figure 1). Another innovative aspect was to use heat available from The cost effectiveness of this project was outstanding. The the interior parking, which was normally exhausted outside, objective was to generate a return on investment of three years to heat the outdoor swimming pool by using a heat pump. with the energy savings. The total cost of construction was This actually improved the indoor air quality in the garages CAN$207,000 before taxes. The building received an inby maintaining a constant slightly negative pressure with sur- centive from the provincial electricity utility of a little more rounding spaces. This recovered energy heats the outdoor than CAN$180,000 while the total annual energy savings are swimming pool, eliminating the need to use energy from the CAN$96,854. This brings down the net return on investment existing water heaters. period to less than three months. Even if no incentive had been Moreover, the energy efﬁciency measures save money for awarded, the return on investment would have been only 2.14 operations and maintenance for the long term. The new vari- years. able frequency drives added on the existing fans will help reThe project’s goal was to reduce energy consumption of the duce belt and fan wear because of the smoother starts, which public spaces, which represents the most important building’s will result in less maintenance, particularly for the cooling monthly expense, by implementing measures on the mechanitowers. As for the new variable frequency drives added on ex- cal systems. Not only did it signiﬁcantly reduce the building’s isting pumps, they will prolong the life cycle of the motors energy consumption, it also increased indoor air quality and due to softer starts and stops. Seven new heat pumps were improved the overall maintenance and operation costs and added in the project, which will add to the maintenance. But schedule. All this was possible at a very low cost and with an they eliminated the use and the maintenance of many electric exceptional return on investment period. Following these imheaters. pressive results, the building’s management company decided Furthermore, all new and existing equipment were linked to to pursue energy-efﬁciency projects in the other condominium a new building automation system (BAS). All sensors, pumps, towers that they manage.
44 ASHRAE Journal
kWh

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December 2012
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