NESHW commercial
Overview
Commercial solar is fiscally viable for all of the same reasons as residential scale solar. Economies of scale will actually improve the return on investment relative to the smaller systems. The best application for commercial solar is domestic hot water preheating. DHW is a year round load and this provides the best payback. Large scale radiant flooring is becoming prevalent and NESHW is currently installing a solar system to heat a 5000 sf floor on the South Shore.
Commercial scale solar hot water systems are a major mechanical systems and as such require professional engineering to detail the roof penetration and attachment techniques as well as to analyze roof and wind loading.
Examples
Below is a photo that shows part of a 300 evacuated tube collector array. This system represents the first use in Boston of solar thermal for a hotel. Here is news release about this project. This collector array is mated with a 659 gallon storage tank filled with 'closed loop' water and large DHW heat exchangers. The roof membrane is EPDM over a wood frame and an engineered attachment detail with an EPDM flashing detail was used.The DHW side was designed to handle a 20 GPM surge rate with only 2 psi pressure drop. This system is displacing natural gas water heating which accounts for about 35% of the building’s total gas usage. The payback is projected at 9 years, and is on track to meet or beat this.
Below is a photo of the racking for part of a large evacuated tube system to supplement electrically heated water in an HUD assisted living complex in Marshfield, Ma. Since the organization is a 501C nonprofit, they were not eligible for tax credits. NESHW initiated contact with Jan Gudell of NSTAR who worked with NESHW to provide funding for the system under a pilot program that NSTAR implemented to evaluate solar thermal.
Below is a photo (courtesy of Purist Energy) that shows the mechanicals of a medium sized domestic hot water preheat for a multifamily building. The large storage tanks are storage for solar preheated water, and the double pumped, flat plate heat exchanger and pump station is mounted on the wall to the right, along with the green expansion tank.
