Steam from the Sun

Steamhead

This is interesting- bet it could be scaled down to district-steam size:

http://www.dailykos.com/story/2015/12/17/1461055/-Now-THAT-S-how-you-do-solar-energy?detail=email

Larry_52

Too bad that these systems attract insects which in turn attract birds which in turn creates "streakers". Look it up

hot_rod

Yeah, now were talking. Nice find.

I did see some residential sized trough collectors intended to generate fluid temperatures to drive absorption chillers for AC. Heat and AC from solar thermal, makes the ROI much more attractive.

BobC

It makes a lot of sense in areas with plenty of sun and open land. You would need a crew to kep the mirrors clean.

Bob

Paul48

A couple month ago, I was reading about a company that was building concentrated solar generators that were sized for residential use. They used a parabolic mirror to focus the suns rays at a Stirling motor/generator. It made 3kw of power, and the temperature at the focal point was 700*, so they got hot water off it for heating. Because it generated power, it was able to track the sun by itself. I got the impression that "big business" was doing their best to put them out of business.

Steamhead

There was actually a device in the early 20th Century called a Heliostat. It was installed at the top of a tall building over a shaft going all the way to the basement. It had a huge mirror which could track the sun and reflect light down the shaft, where smaller mirrors would grab some of the light and distribute it to the rooms. If there was no sunlight, auxiliary electric lights were used. Some versions had devices which cleaned the mirror automatically.

When was the last time any of us saw a Heliostat?

hot_rod

I think ME has talked about a heliostat at NREL in Colorado?

Steamhead

Here's the one I read about a long time ago- patent granted in 1938:

http://www.freepatentsonline.com/2135997.html

Paul48

We really need to re-visit the thinking that made that. We sit in our houses on beautiful, sunny days, and have electric lights on. The same interests that kept Tesla from giving power to humanity, for free, are preventing the advancement of technologies they can't profit from.

Jamie Hall

Just so long as the mirror thingy can work as an umbrella I'm fine with it. On the long term average where I live we get three hours of sunshine per day, averaged over a year.

Mark Eatherton

hot rod said:

I think ME has talked about a heliostat at NREL in Colorado?

High up on Table Mesa in Golden Colorado, SIggy and I were getting a back alley tour, and they took us to their "Accelerated Solar Exposure Lab", where they have a sizable heliostat. They had just gotten done melting a brick for a group of young students when we walked into the lab. Stunk to high heaven.

Unfortunately, solar PV is considered far more sexy because it can spin the meter backwards, and solar thermal is taking a back seat to the PV technology.

What a lot of people don't realize is that solar thermal can be as much as 80% efficient, compared to PV at 20% on a good day. So environmentally speaking, solar PV requires 3 to 4 times as much solar panels than will ST, and the production of crystalline PV cells comes with a BIG environmental impact on the Earth. Even our government (DOE) is favoring PV. Follow the money... The recent tax credits will degrade for ST much faster than other environmentally harmful technologies. One part of the sham is that the performance of PV will degrade over time, whereas ST remains constant through the life of the solar collectors.

Even if you couple PV with an air source heat pump with a COP of 3 to 1 in an effort to boost its efficiency, it can't exceed ST.

Apologies for the rant...

ME

Paul48

Jamie..........Connecticut or England?

Jamie Hall

Paul48 said:

Jamie..........Connecticut or England?

Connecticut. Where part of my family lives, though, in Scotland (Orkney) is worse...

And on Mark's comment -- he is so right! Solar thermal really does work -- even here in cloudy Connecticut. Solar PV? Well, if you can afford the batteries...

gbourozikas

Anything that requires a ton of maintenance (Heliostat) or is not yet safety-proofed-for-the-house (Solar Thermal) is a poor choice for residential and even small buildings. I have high hopes for fiber waveguides, bringing sunlight into hard-to-reach rooms and corners of the house. See, for example, this poorly designed website for some of the major players:

brightenyourhome.net/Hybrid-Solar-Lighting.html

Brewbeer

When PV panels get hot, and they do get hot, their output decreases. Keeping the panel cool with water makes sense. Someone needs to design a PV panel that can also produce hot water to be used for SH or DHW, either directly or through a heat pump.

SWEI

Several such designs (sometimes referred to as PV-Thermal or PV-T) have been produced during the past decade or so. None has really managed to gain traction, as the costs have been far higher than the market will bear.

Steamhead

gbourozikas said:

Anything that requires a ton of maintenance (Heliostat) or is not yet safety-proofed-for-the-house (Solar Thermal) is a poor choice for residential and even small buildings. I have high hopes for fiber waveguides, bringing sunlight into hard-to-reach rooms and corners of the house. See, for example, this poorly designed website for some of the major players:

brightenyourhome.net/Hybrid-Solar-Lighting.html

George is one of our steam customers. Welcome to the Wall, George!

Unknown

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SWEI

Solar thermal DHW preheat pencils out for a LOT of locations. Fuel cost only drives part of the ROI math. The other big term in the equation is operating hours, which is where even a partial preheat can really show its stuff.

Unknown

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jumper

It's all about temperature with solar thermal. With high enough temperature you can heat up the earth beneath a building to draw upon when needed.

hot_rod

The holy grail for solar thermal is the storage. It's expensive to try and store large quantities of thermal energy in tanks. The ground is an option.

Solar passive operation doesn't cost a penny, early cave dwellers knew how to take advantage of that concept.

You could consider ground source HP, in heat mode as solar driven energy converters. Drakes Landing, Weller School, and several others have proven using solar to preheat the ground, or injection wells leverages the HP efficiency.

For best solar heating look for the lowest possible temperature, heat emitters, Jaga radiators are a good example

One of the most efficient solar thermal DHW systems is at a bottling facility in Tempe AZ. They just pre-heat to around 100- 110, this drives the collector efficiency way up, and minimizes the gas boiler operation.

Un-glazed pool collectors will run mid 80% efficiencies when ambient and fluid temperature are close, very little loss to the surrounding air. Pool collectors still prove to be a viable business, look down the next time you fly into Florida.