A heliostat reflects the sun to a fixed spot. To do so it has a mirror, moveable
in two axis. A straighforward way to build one is using two servos
as is done here. The material costs
around 20 Euro per heliostat (retail price, servos included). The
size of the mirror per heliostat has relatively little influence on the
costs and on the construction.
I have not included in this calculation the costs of the mounting frame
and the electronic (a micro-controller plus an additional circuit)
which must be amortized over all controlled heliostats.
I use standard products from DIY superstore (Baumarkt) and Conrad electronic store.
For the micro-controller I use Arduino,
an inexpensive, open source platform, easy to use.
When I designed the heliostats I thought much about costs. Especially following sites were helpful to me: First that of Erik Rossen, and his problems with getting a price for small gears. It is difficult in a DIY environment, to calculate an en gros price, assuming the construction of a large number of heliostats, not just a dozen. My conclusion is that the small gears must be already contained in RC-servos. They use a well developed technology and are fabricated automatically in large quantities; (the prices of) the gears are all contained in those black plastik boxes. Some people asked me: "Why didn't you consider stepper motors instead?" I did, but on the whole rejected them for DIY-heliostats for the above reason. So my design follows the properties RC-Servos and uses otherwise inexpensive, readily available material like styrofoam (XPS).
The second important piece of information was that of
Duane C. Johnson who maintains a vast list of links to various
solar concentration devices. He cites as a rule of thumb that
the installation costs for any system should be less than one dollar
per Watt generated, to compete against conventional power plants.
As it is only a rule of thumb you can replace dollar by Euro.
A recent powerplant in Spain
(PS10)
using heliostat technology gets only a ratio of 3 Euro per
Watt.
Check out the heliostat construction and learn how to build one yourself.
The control of the heliostat is the
Tracking System.
Currently, I work on calculated trackers; that is azimuth and elevation
of sun is calculated from date, time and geographical latitude and
longitude. You can download a program for Arduino from my Solar Arduino Tracker project at Happylab (a nice place to make things, btw) When you
plan some serious project with heliostats I would be interested to hear
about it. Input from new projects always helps and it may be possible
to design something special for your needs or give you general advice.
Author: Hannes Hassler. I will be interested being contacted about projects using this or similar technology, price/energy considerations, architecture and arts projects, stirling motors and especially about solar desalination.