Even when equipped with a roof full of solar modules to provide your home with energy, a severe weather event can disable the power grid infrastructure, preventing a grid-tied solar inverter from producing energy.
As a result of this intermittent “down time” the SURE HOUSE team used this as an opportunity to develop an integrated system to provide a domestic hot water solution that is both sustainable and resilient. Our innovative system hybridizes a photovoltaic electric hot water system and an integrated heat pump hot water heater. Each system alone provides an efficient solution for generating hot water however; it is the combination of these two systems together that creates an innovative solution that truly makes it both sustainable and resilient.
Provided with enough sunlight, the primary domestic hot water source is a standalone photovoltaic electric system. This system consists of series of dedicated solar modules that are integrated into the storm shutters located on the southern deck, and a control unit and heating element at the hot water tank. This PV electric hot water system represents a completely independent electrical system replacing a conventional fluid-based solar thermal system.
According to the third edition of a jointly written report on PV pricing trends from the U.S. Department of Energy (DOE) National Renewable Energy Laboratory (NREL) and Lawrence Berkley National Laboratory (LBNL), the price of distributed solar photovoltaic systems dropped by 12-19 percent in 2013, and is expected to continue to drop another 3-12 percent in 2014. As component and installation costs decline, photovoltaic systems become cost-competitive alternatives to solar thermal collectors. The simplicity and durability of a PV electric system also presents operation and maintenance advantages that fluid based solar thermal systems do not.
Even though both systems are performing the same task, (using energy harvested from the sun to heat water), the SURE HOUSE PV Heat Pump Hot Water System is competitively priced when compared to a conventional solar thermal system. However, it offers a higher level of durability, a lower level of maintenance and provides an overall more resilient system for homeowners in coastal communities. Instead of traditional flat plate or evacuated tube solar collectors, susceptible to environmental damage, the PV electric system uses strings of durable and lightweight building-integrated PV. The harvested energy is then transferred in the form of direct current to the PV heater control unit and the heating element. In this system, the PV heater replaces the fluid loop modulating the available direct current through a resistance coil to deliver the maximum heating energy to the domestic hot water tank.
The greatest benefit of this system is the fact that the flow of electricity and energy produced in this system allows you to provide power to your home when provided with sun, even when disconnected from the grid.
As fitting as the PV electric hot water system already is for coastal communities, what makes this system even more desirable is its coupling with a high efficiency heat pump as its secondary source of energy. In many cases, when you need to resort to a secondary heat source, the next line of defense is a traditional resistance coil that would draw a large amount of electric energy to heat water. In the SURE HOUSE system, this backup device is a highly efficient heat pump which is only triggered when the sun cannot provide enough energy to keep the water temperature above a certain set point. The heat pump consists of a loop containing a fluid with a high thermal capacity, giving it the ability to store a great amount of energy. This energy is then easily transferred to the hot water tank due to the high surface area of the loop before it is sent back to the heat pump to be reheated. Even when in heat pump mode, our hot water system will still use 70% less energy than a standard electric hot water heater.