Outdoor pool installs solar panels to heat water and conserve energy

by habiba_abudu | January 29, 2020 2:38 pm

By Daniela Paraschiv

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The City of Mississauga’s commitment to lead and encourage environmentally responsible approaches is demonstrated through its numerous programs, which promote energy-efficient technologies, best practices for resource conservation, production of renewable energy, and reduction in emissions and waste. One of the many initiatives includes installation of solar panels to heat outdoor pools, which has greatly reduced energy usage, greenhouse gas (GHG) emissions, and energy costs.

Renewable energy is generated from resources, such as solar, wind, geothermal, biomass, water, etc., that are naturally replenished at a rate equal to or faster than they are consumed. The city is actively pursuing ways to harness solar energy, such as implementing photovoltaic technology, which uses solar cells to convert sunlight directly into electricity and solar collectors or panels that are used to heat water or air in aquatic facilities.

Boiling down to an energy-efficient technology

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In 2017, the City of Mississauga commissioned Ian Sinclair, a specialized consulting engineer, to assess the feasibility of installing a solar water heating system at one of its outdoor pools. All seven outdoor pools in the city were evaluated for usage, roof condition, orientation, etc. The Lions Club of Credit Valley outdoor pool was selected for the pilot installation. This 12- x 24- x 1.6-m (40- x 80- x 5.4-ft) large facility is usually filled with water by the end of May. Swimming begins in early June and continues until approximately the first week of September.

The solar water heating system at the facility uses 28 (1.2- x 3.6-m [4- x 12-ft) unglazed collectors, chosen for their simplicity, robustness, and ease of use. These thermal panels are designed to heat pools and are not covered in glass, allowing the sun to shine directly on the rubber or plastic matting. This is especially effective when heating outdoor pools during the warm summer months, as none of the sun’s heat is reflected away by the glass. While the equipment can generate higher temperatures with great efficiency, its advantages are most noticeable in colder months, which are outside of those of a pool that is only operated during the summer.

On the other hand, glazed thermal panels comprise aluminum frames covered with tempered glass. A series of copper tubes run under the glass through which water or antifreeze runs. The glass insulates the copper as the sun warms them by preventing the heat from escaping to the colder, outside air. These are efficient for heating hot potable water for a home, as they can surprisingly collect a lot of heat, even in February on cold sunny days.

That said, the additional piping and storage complexity of a glazed collector system, along with the need for a heat exchanger, was considered unsuitable for this project. Costs were also a significant factor: unglazed collectors are a budget-friendly solar thermal technology; therefore, they were selected.

Design philosophy

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Unglazed collectors are permanently filled with pool water during the summer season and are drained when not in use. When solar energy is available and of useful grade—as determined by comparing the temperature of a roof-mounted sensor with the pool’s return water sensor, using a dedicated controller—a solar pump is enabled, drawing a fraction of the pool’s main pumping volume and diverting it through the roof-mounted collectors. This water mixes with the main pool feed on return and the existing boiler/heat exchange system is used to bring its temperature up to the required set point. As such, this is considered a supplemental source of heating. An EnerPool simulation software helped determine the system was capable of delivering approximately 47,000 equivalent kilowatt hours (ekWh) of energy per year.

Implementing the design

After being tendered to pre-selected bidders, the system was finally awarded to Solcan Ltd., in London, Ont., a specialist, design-build contractor with experience in solar thermal technology for indoor and outdoor pools.

The implementation of the solar water heating system took nearly a month. The city installed a separate control system—that monitors the solar equipment—to measure the device’s performance. The main features of the heating system are:

• A flow meter, which measures the flow of water through the solar loop and records it on a local screen.
• The supply/return temperature sensors. The multiplying flow of water and its temperature variance across the solar supply/return loop results in a calculation of energy generated by the solar loop, which is used to calculate the system’s performance.

Performance verification

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The data analysis on June 11, 2018, showed the system generating a peak output of 74 kW (102 hp). Based on the collector’s performance curve and a pool temperature of 26 C (79 F), this number meets the expected peak system power output as per the Solar Rating and Certification Corp. (SRCC) certified performance curve. The SRCC is a standard measurement certification process that calculates the expected peak thermal power generation based on solar gain, fluid temperatures, and flowrates.

The data for nearly two-and-a-half weeks of operation showed an average daily production of 466 ekWh of energy, which resulted in a monthly output of 14,446 ekWh. According to the original simulation completed in July, as part of the feasibility study, the anticipated energy generation was 14,889 ekWh. This meant the system was performing as expected.

Operation and maintenance

The system only requires filling and draining seasonally. The collectors must not contain water outside of the operating season (May to September), as freezing may damage the collectors beyond repair. At the end of the season, the collectors are drained via gravity at the purpose-built drain valve in the northwest corner of the building.

References:

• Commissioning Report for Lions Club of Credit Valley Outdoor Pool Solar Retrofit Project, July 27, 2018, by Ian Sinclair, P. Eng. Project Consulting Engineer.

[5]Daniela Paraschiv is the manager of the energy management section at the City of Mississauga. She is a licensed professional engineer of Ontario, a project management professional, as well as a certified Lean Green Belt practitioner. With more than 25 years of experience in the energy sector, Paraschiv’s approach to conservation starts with engagement of the stakeholders responsible for buildings and sites operation. She believes the key to achieve sustainable energy savings is tapping into people’s desire to embrace innovation and the willingness to accept the challenges of a new start. As changing the status quo requires time and perseverance, Paraschiv is committed to finding ways to transition to a new mindset which supports sustainability at all levels. She can be reached via e-mail at daniela.paraschiv@mississauga.ca.

Source URL: https://www.poolspamarketing.com/trade/features/outdoor-pool-installs-solar-panels-to-heat-water-and-conserve-energy/

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