Thermal Solar Collection Tubes That Provide Hot Water Year-Round

On the roof, amidst an array of native wild grasses and shrubs, six banks holding 180 small thermal solar collection tubes provide hot water year-round. This new technology, made by Apricus Solar Company, is less common than the flat solar plates often used for thermal heating.


1. Evacuated tubes: A set of double-walled evacuated glass cylinders sit side-by-side to form the solar-absorption mechanism. They can hold heat up to 304 degrees Fahrenheit while remaining cool on their exteriors.

The Boglis love the self-reliance afforded by generating thermal energy and growing a garden on their roof.

The kitchen looks out onto a broad patio and backyard through floor-to-ceiling glass, while the upstairs balcony provides shading to allow in only diffuse daylight.

2. Heat pipes: Inside the glass tubes, hollow copper shafts transfer heat using pressure and condensation.

The driveway has a permeable surface.

3. Header pipes: Hot vapor travels through the shafts to the heads of the pipes while condensed liquid drops to the base. The headers form "plug" attachments for easy insulation.

White says of the living room, "We just blew it wide open," removing walls to create a bright, continuous space.

4. Insulation: The headers are wrapped in moldable, nonflammable, lightweight glass wool insulation.


1. When sun hits the evacuated tubes, it is absorbed and converted into heat.

2. The internal copper pipes move the heat to the copper headers.

3. Each heat-transfer cycle raises the water temperature in the tank. The tubes are coordinated with a radiant floor system and two heat exchangers recapture heat from used hot water.

Direct heat transfer from the tubes to the tank distinguishes this technology from a flat panel, which can lose heat to the atmosphere due to the method of insulation. Erlandson estimates the payback on photovoltaic (PV) panels would have been about 20 years. "And most systems only have about a 25-year life span," he adds. The thermal collectors will pay for themselves in savings within ten years and will last at least twice that long. What’s more, they take only about nine weeks to erase their carbon footprint, something PV panels (made with an array of chemicals) can’t claim. 


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