The Learner's Heliostat

Description

The main problems with making greater domestic use of sunlight are clouds and the Earth's rotation. To begin tackling the second problem, I built a heliostat prototype, pictured. A heliostat is a big, pivoting reflector that keeps the sun's image falling on the same spot all day (e.g., a window or photovoltaic panel) despite the Earth's rotation. The close-to-finished project is the main gallery image, which shows a West-facing kitchen window getting sunlight at 9:30 AM. The materials of construction maximize the use of wood, to minimize the carbon footprint of the project itself. Wind and water resistance were major design considerations. Another was adaptability to diverse installation situations. I aim for automatic, computerized control in a future embodiment, to be fitted to the present project. The computer may be programmed to protect the heliostat from high winds by placing the reflector horizontal; ice and snow, vertical. The project may thus become robot-like.

Details

The background photo shows an art installation in Ottawa that looks heliostat-inspired.

Relevance:

“Residential energy use is responsible for about 20% of total greenhouse gas (GHG) emissions in the US.”

From

https://wcec.ucdavis.edu/analysis-of-greenhouse-gas-emissions-from-residential-heating-technologies-in-usa-2/

Last accessed 6 Nov 2022.

Figure not found in a peer reviewed source but probably partly based on

Dichter, N., & Aboud, A. (2020). Analysis of Greenhouse Gas Emissions from Residential Heating Technologies in the USA. UC Davis Western Cooling Efficiency Center. https://wcec.ucdavis.edu/wp-content/uploads/GHG-Emissions-from-Residential-

Comment:

The carbon emissions on these shores appear to be roughly evenly distributed across sectors. (See: “Overview of greenhouse gasses”, publisher: EPA, govt, USA) Therefore, meaningful reductions will require a combination of collective action and household-level action: neither will suffice by itself.

From Zig Ziglar, we have this: “Whatever you need to do, do a little every day.”

Safety:

Do not use warped plywood for the reflector or it may focus sunlight and cause a fire. Replace or reverse it if it becomes warped. Waterproof it carefully before putting it into service. Inspect for foci periodically and after each rain and renew or reverse the reflector if any are found.

Linseed oil safety:

https://www.simplemost.com/linseed-oil-can-fire-hazard-need-know-stay-safe/

https://www.flinnsci.com/sds_450-linseed-oil/sds_450/

Build, miscellaneous:
I use push-rods made of wooden dowels to set the angles. These can be marked with a pencil to show the daily series of settings that must be reproduced by a future computerized controller. The dowel can be rotated to get a fresh surface for marking the results for the following month. In future, each dowel will be replaced by some electric device such as a car's cable-type power window regulator, illustrated below. The system diagram shown in the gallery is proposed and not built.

Dowel hardware — The manual clutch assemblies for the fixed ends, which are based on conduit clamps. The adjustable ends are very similar. In addition, each dowel passes through a guide assembly with a slip fit. The dowels have one-hole sections of mending plates on the ends to keep them from getting pulled out of the clutch by gusts of wind.

The manual clutch assemblies for the fixed ends, which are based on conduit clamps. The adjustable ends are very similar. In addition, each dowel passes through a guide assembly with a slip fit. The dowels have one-hole sections of mending plates on the ends to keep them from getting pulled out of the clutch by gusts of wind.

Components

2 × plywood sheet 4' x 2' x 0.5"

2 × pushrod dowels 0.75" dia. x 48" long

1 × wooden block, for joining pieces at 45 degrees 6" x 1.5" x 1.5"; cut into 4 wedges, 3" long, with a 45 dgree angle.

2 × long carriage bolts, with matching nuts and washers 1/4" dia. x 2" long

19 × short carriage bolts, with nuts and washers 1/4" dia. x 1.5" long

Build Instructions

Collapse

Cuts required

The plywood product I used was 1/2x2x4 G1S, $37 ea before tax in Ontario in summer of 2022. For the project infrastructure, four 1" x 4" x 8' knotty pine planks would be price competitive and less work to waterproof, but less convenient to transport. They may have a stiffness advantage, being thicker, and be less prone to stripped threads.

One of the plywood sheets is for the reflector and the other is to be cut lengthwise into eight 4-foot strips 3” wide to make the base and universal joint assembly (UJ). Each sheet weighs 5 kg (11 lb).

From the strips, cut the following 24 lengths, all in inches. The UJ hypotenuse is chamfered on one long edge on one end.

Dowel lengths: azimuth, 30"; elevation, 34".

Length, in	Part no.	Function	Strip number (shows suggested tiling)
3	7	Spacer for diagonal base brace	1
6	18	Spacer for elevation motor paddle	1
6	17	Elevation motor paddle	1
6	17	Azimuth motor paddle	3
11.5	14	UJ side	3
12	3	Horizontal crosspiece	2
12	15	UJ side	3
16.3	16	UJ hypotenuse	3
11.3	10	Left vertical brace	4
19	9	Diagonal base brace	4
24	6	Cross base element	5
24	4	Cross base element vertical	5
24	8	Side base element	6
24	5	Side base element vertical	6
14.9	11	Right vertical brace	4
30	1	Left vertical strut	2
30	2	Right vertical strut	1
48	19	Hinge strip for attaching reflector	7
2.625	20	Azimuth spacer	scrap
48	21	Reflector	Sheet 1
24	22	L strut reinforcer	8
24	23	R strut reinforcer	8
6	24	UJ gusset plate	scrap
3	28	Rear caster spacer	Scrap, width = 2.75”

Other wooden parts:

18	25	Base brace reinforcer	1.5 x 1.5” x 24” hdwd
12	26	Body diag. upper	1.5 x .75” pine scrap
10.25	27	Body diag. lower	“

2
Detailing for fastener placement
Excuse the amateurish Powerpoint CAD.
- The big disks are carriage bolts and a foot.
- Small rectangles are furniture brackets.
- The UJ triangle will use a wooden block in each corner for fastening.
- The vertical braces will both use furniture brackets with their angles widened as necessary in a drill press vise.
- The right brace will use a connection block at the lower end instead of furniture braces, because I wanted to use up the fourth block, which are made in pairs.
- The heads of the carriage bolts face the reflector.
- The crosspiece is in front of the verticals when you stand behind the reflector.
- The UJ hinges go on the front of the crosspiece and outside the triangle of the UJ, at the bottom of a side of the triangle.
- The base brace and spacer are not shown in the napkin sketch.
3

Miter-box cuts (mostly 90 degrees but precise)

Frame the UJ as shown except that the chamfer is on the wrong end.

Complete the cuts and keep an eye on the humidity. I gather that for best results, you condition all lumber in the room where it will be cut (done) and cut everything the same day. (Or at least at the same humidity?) Right after cutting, I sanded all edges and corners, (outside and while wearing gloves) because I was getting tired of infected splinters. I put on a P100 respirator halfway through sanding. I finished by brushing off the sandings with a new shoeshine brush. Now everything I cut feels like a wooden kid's toy.