Chapter 12: Alternative Technologies To be used with the Guide to Building Energy Efficient Homes in Kentucky

Alternative Technologies

Solar Hot Water Key concept: Reduce gas or electric requirements to produce hot water Use sun’s energy to heat or preheat water

Solar Hot Water System Solar Collector Storage Tank Solar Hot Water System

ActivePassive

Systems Active Relies on pumps and valves to circulate the water or heat exchange fluid through the solar collector Passive Relies on the natural tendency of water to rise when heated, and thereby circulate through the system

Systems Active Slightly more complicated More flexible in placement of the components Passive Simpler – Lack of pumps Placement of components dependent on the physics of hot water buoyancy

Direct Systems

Closed Loop Solar Hot Water System Drain Back System

The drain back system uses water as the heat exchange fluid – Freeze protection – pump shuts off when the temperature of the collector cools below that of the tank Water “drains back” into storage reservoirs

Passive Systems Thermo-siphon system uses the tendency of water to rise as it is heated.

Passive Systems Cooler bottom tank water flows down pipes to bottom of collector Heated water becomes lighter and flows up and into the top of storage tank

Passive Systems The integral collector storage system has the storage tank integrated into the solar collector.

Passive Systems Cold water supply is connected directly to the collector Sun heats this water, which remains in the panel until needed

Design Considerations Solar collectors should be placed on the south side Install a mixing valve Install a back-up heat system

Photovoltaic Panels Photovoltaic (PV) panels are a way to generate on-site energy High cost

Photovoltaic System

Design Considerations Design of PV systems can affect the performance Location Angle of the collector Internal losses Shading Temperature

Design Considerations Variations within 15 degrees of true south – OK Beyond 15 degrees – lose performance Set the tilt to maximize the summer solar incident angle Difficult to do if considering aesthetics

Design Considerations Locate panels in shade- free areas Panels need to be clean of dust, leaves, snow Temperature affects the performance of the PV panel – Keep as cool as possible

Summary