A rooftop device to track the sun using two small motors controlled by a computer, directing more daylighting into a building's interior throughout the day as needed.
Heliostats are computer-controlled flat mirrors which use an on-board micro-processor to keep the sun reflected on a fixed target as the sun moves across the sky. Heliostats are a potentially low cost way to capture light and heat and provide reflective daylighting by directing it into a building through windows or skylights. Heliostats placed outside cold and dark rooms can increase comfort by providing daylighting and directing warmth into the room. Multiple heliostats can be used to warm a single room, or simultaneously warm different spaces. Heliostat supports are available in various wind ratings.
Potential building applications include schools, office buildings, homes, industrial workspaces, and farm outbuildings.
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Baseline Description:
Wikoda, Inc. notes that their Heliostat reflects up to half a square meter of sunlight and provides up to 500 Watts of sun energy (the equivalent of 50 traditional 60-Watt bulbs). Based on a typical $0.15 per KWhr cost of electricity, the Sunflower Home Heliostat can provide the equivalent of $2 per day of free natural lighting each sunny day. On a yearly basis, the Sunflower Heliostat provides $200 to $600 of free lighting per year depending on local sky conditions (Shahan, 2012). (Note that this example involves the offset of constant lighting provided by incandescent bulbs. Savings are greatly diminished when LED lighting is available and when one considers the hours per day for typical home lamp use---the mean residential lighting on-time is about 1.7 hours per day).
The "Sunflower" has a cost of $299. Their website claims that they are the only heliostat available for a price less than $1,000.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Zachary Shahan, 04/19/2012. Home Heliostats---Say What? CleanTechnica
Technical Advisory Group: 2014 Commercial Building TAG (#9) TAG Ranking: 40 out of 44 Technologies (2014 Commercial TAG strategies ranked separately) Average TAG Rating: 2.11 out of 5 TAG Ranking Date: 03/17/2014 TAG Rating Commentary: Interesting concepts but not likely to be cost effective or find widespread use. Heliostats are components of larger systems that include technologies to transfer the captured sunlight and also to distribute them in interior spaces. There are many different options that have been designed as parts of whole systems. Their performance depends on the rest of the system. They have not yet been proven widely, with mostly demonstration installations. CLTC has tried three systems in the past, is currently testing a fourth and expecting a fifth within the next few months. So far we have not realized successful performance with the ones we have tested. We will know more towards the end of the year. These are great but I think there are more cost effective daylighting strategies that need market uptake. Applications for this technology are probably limited. The technology is sound, but probably not widely implementable. Again a solar dependent technology - depends on generous availability of sunlight to justify the cost.