[walrus01]

On a large scale motorized sun tracking photovoltaics is very costly. The systems that can take the wind loading of six 1.65 x 1.00 meter size 60-cell panels on a pole cost more than the panels. Needs like a 6" OD sch80 pipe set into a concrete foundation.

Commodity fixed angle ground mount photovoltaics arrays are low cost.

If you do the dollar and kWh produced in year calculation for spending $40,000 on fixed mount ground pv, and $40k on a combination of pv panels on trackers, and compare the kWh proxied by both... The fixed ground mount comes out far ahead.

A tracking mount can make sense only if you have a VERY small amount of space to work with and want the absolute most kWh per month per square meter of area occupied on the ground. And don't care about money much.

[usrusr]

Heliostat installations used to be common when panels were so expensive that spacing them out wide enough to keep them from shadowing each other when angled for dusk/dawn made sense. Now heliostats are only done in exceptional situations, for example I've seen some that didn't seem to be particularly old on rugged terrain were the quantity approach would be costly as well and easy foundation opportunities are sufficiently far from each other to prevent peer shadowing anyways.

But I do wonder if heliostats might see quite a revival in agrovoltaics: there, you want a certain distance between panels anyways, and perhaps the plants won't mind if you steal a little more light off-noon in exchange for less shadowing at noon. Electricity supply/demand would certainly applaud this bias, in a market with lots of photovoltaics a Wh at noon is certainly worth less than those closer the the periphery of the daily sun cycle.

And if you do agrovoltaics right, the structure will be expensive anyways (making the markup for heliostat insignificant) because imho it's still just an unfinished prototype if the structures for holding the panels aren't designed to double as an overhead rail system for farming powertools that could become a considerable efficiency gain over the century-old game of tractor vs mud.

[taneq]

Yeah, exactly. Tracking photovoltaics used to be worth it back when photovoltaics were $5 per watt. The price has dropped so much that even for fixed angle ground mounts, the mounting frames and labour to install them costs far more than the panels themselves. Sun-tracking is just not economical compared with cheap static panels.

(I spent quite a lot of time on an idea for rooftop solar thermal power and was trying to build a prototype when the solar panel prices started crashing. It pretty soon became inescapable fact that small scale solar thermal with all its moving parts just wasn't viable any more. I'd be surprised if even the large mirror-farm CSP is competitive these days.)

[usrusr]

Thermal for heating/hot shower or thermal for some adventure in driving a generator?

For heating, photovoltaics supplying a heat pump is starting to give direct thermal a run for the money (well, not actually for the money yet, direct thermal is still cheaper, but at least in terms of how much you could harvest from a given roof area)

If money isn't an objection at all, e.g. if you strive for that sense of achievement of a good setup, there are hybrid modules that pick up the 20% or so photovoltaics achieves and still funnel the remaining energy into heating a liquid medium.

[taneq]

This idea was a flat "panel" of parabolic reflectors focused on heat exchanger tubes, driving a heat engine. The new bit was that the heat engine was going to be open loop (basically Brayton cycle with the compression stroke pushing air into the heat exchanger and expansion stroke driven by heated air from the exchanger) so its power density would have been much higher and cost lower than the usual Stirling cycle engines which cost a ridiculous amount for what they are.

I had all the thermodynamics worked out and it would have been something like 5x as cost effective as photovoltaic. Then the cost of photovoltaic panels dropped 10x in a year. C'est la vie, at least my roof is covered in PV now. I've thought of running some tubing under the panels to pre-heat water for our solar hot water system but these days it's scarcely worth the bother (at least where I live which is pretty much perfect for solar power.)

[snickmy]

There are hybrid solution of panels that are basically layering a PV over a Thermal Panel (pipes with fluid inside). I never saw them getting massive traction. I wondered why.

Some example: https://www.convertenergy.co.uk https://dualsun.com/

[xxs]

Gotta admire the effortless mix up of metric and imperial units.

[Kaibeezy]

1885 - invention of process for seamless steel pipes from bar stock, Development History of Seamless Steel Pipe, https://www.supplychainquarterly.com/articles/3787-the-devel...

1954 - first practical silicon solar cell, Timeline of Solar Cells, https://en.wikipedia.org/wiki/Timeline_of_solar_cells

[0_____0]

the US is a metric country that's in denial

[xboxnolifes]

The US is a country that just does the engineering and doesn't constantly whine when they see a unit they don't like.

[xxs]

Reminds me of a bug in a certain laptop docking firmware that considers TjMax of 95F (instead of 95C) and running the CPU at full throttle mode (like 400MHz) at all times.

[0_____0]

it only loses us a billion dollar spacecraft once in a while

[walrus01]

if you're buying construction supplies in north america you're not going to get metric sized pipes for like, sticking a robust mast in the ground.

whereas 54, 60, 72-cell pv panels with aluminum frames made from 156mm cells are manufactured in metric dimensions.