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THE Solar Thermal Energy Thread (merged)

Discussions of conventional and alternative energy production technologies.

Dismantling old solar water heater

Unread postby papa moose » Mon 07 Feb 2011, 23:26:29

Folks, i'm looking for some advice to guide me in my attempt to remove some old solar panels from the roof of my house.
History:
Our house was built in 1979 and either during construction or at some later date a solar hot water heater was added to the northern roof. At some point the previous (original) owners decommissioned the solar panels and installed an electric cylinder (i suppose the cylinder ID will give a date of manf. but i have never thought to look).
Problem:
In the past few weeks i have spent a lot of time on the roof (and inside it) as i have been installing ceiling batts/insullation, i have decided to remove the old panels for two reasons; firstly, i need to do so to access the roof space beneath them which i cannot reach from any direction other than above. Secondly, i have noticed that the panel supports that hold the panels to the roof structure are severely corroded (of the four supports two look okay, one is quite rusty but the fourth no longer exists in any meaningful way) this is causing the whole panel assembly to droop and could theoretically result in a failure seeing the panels fall off the roof with associated chaos and mayhem.
Panel Description:
As best i can tell the external frames are riveted aluminium sheet metal with either a perspex or glass lid. The internals of the units look similiar to a oil radiator, two sheets of copper(?) pressed together with plumbing fittings to allow water in one side and out the other, there are three panels plumbed together in the system. Just looking into the panels from above it appears that the copper sheets are lying ontop of some fibreglass(?) insulation. There is no tank attached to the panels so i assume they were some type of split system previously, with a tank and pump situated on the ground nearby.
Current Plan:
As i have no idea how much these panels weigh and don't have a crane handy i am planning to dismantle each panel on the roof and then lower the components one by one.
My biggest concern is that the insullation underneath the copper could be asbestos.
Does anyone have any knowledge on materials used to manufacture solar panels in the late 70s, or any other useful advice?
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Re: Dismantling old solar water heater

Unread postby steam_cannon » Tue 08 Feb 2011, 10:11:53

Image

Methods you could use:

1. Hard work, that's how it got up there. You'll need a ladder, a hand held Circular saw and Metal cutting blades. Lay cloth on the roof so the pieces don't cut up the roof. Cut chunks out that are small enough to handle standing such that gravity does not make the saw or metal fall on you. Take it apart as much as possible first. Try to set up a safety rope and harness so you don't fall of the roof, connect the rope to a car or sandbags on the other side of the building if there are no anchor points. Ask a buddy that climes rocks to help.

2. Call a local roofer and get an estimate.

3. Build a clever framework and ropes to lower the system to the ground.

4. Offer it for free, removal required.

Here are a few links with tips and advice. These are the best links I found on the topic. They talk about the problem, but none of them actually tell you how to remove a solar water heater from the roof, besides hard work or calling a roofer.

Links:
How to Remove Solar Water Heater Panels From a Roof
Should I remove solar panels or get a solar hot water heater?
uncertain of how to remove solar panels that sit on your customer's roof
Remove old solar hot water system from roof
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Re: Dismantling old solar water heater

Unread postby papa moose » Tue 08 Feb 2011, 19:47:29

Thanks for the links, i like the idea of advertising it "free, to be removed".
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Re: Dismantling old solar water heater

Unread postby Frank » Sun 13 Feb 2011, 07:45:02

I've worked on several and have always seen f-glass insulation used.
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Re: Dismantling old solar water heater

Unread postby PrestonSturges » Sun 13 Feb 2011, 09:57:26

It's just as important to have a rope on the panel. You want the situation stabilized at all times.
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Re: Dismantling old solar water heater

Unread postby Frank » Sun 13 Feb 2011, 21:44:16

Absolutely. Three of us removed two flatplates once as part of a tube installation job. Two guys were each on their own ladders to walk it (one panel at a time) down and I sat on the peak with 2 ropes tied to each end of the panel. It was pretty straightforward to lower it down in a controlled fashion.
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Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Wed 18 May 2011, 00:56:58

Hi,

I have come up with a design for a cheap solar thermal collector. I have posted it on this site:-
http://openfarmtech.org/forum/discussion/196/a-two-lens-design-for-a-cheap-solar-thermal-collector




The system shown in the first attached diagram can be used as a concentrating solar thermal system. The object is to achieve a concentration ration of 100:1 to run a stirling engine using as little expensive materials as possible.

• It uses a transparent plastic or glass spherical container that act like a spot lens when filled with water. The lens focuses a large amount of sunlight at its focus.

• The focus of this lens would be a small spot, just like a parabolic dish. We have to place another small spherical water lens controlled by a microprocessor close to this focus.

• The combination of a large and a small spherical lens would be used to focus light at a single spot. The effective concentration ratio would be very large.

• Since the focus lies below the lens, one needs to take care that the lens is placed at a sufficient elevation so that there is enough room for the small lens and the striling engine to move throughout the day and still focus light on the engine.

• This system acts as a cheaper alternative to expensive dish-sterling systems.

The weight of the larger lens could be a concern, since it is a large sphere filled with water. In order to reduce the weight, the following design shown in the second diagram can be used.


Two concentric transparent spheres with water filled in the space between them can be used as a lens. It will significantly reduce the weight.


Advantages of the lens collector over the Dish Collector:-

• It eliminates the need for a reflective glass surface completely. The highly reflective glasses used in the contemporary designs are very expensive and represent a significant part of the development cost. This design could bring down the cost significantly.

• In the Dish collector, it is required that the entire dish has to track the movement of the sun continuously. This requires giant heliostats, motors etc. But in the lens collector, only the small lens and the stirling engine has to be adjusted according to the movement of the sun. It requires cheap microprocessors and small motors that can be programmed easily.

• The round shape of the lens and its weight provide better protection against strong winds than the large dish shape.

• The lenses can be filled with sea water, since it is not corrosive to plastic. So a vast unutilized resource can be used to generate electricity. There is no need to use fresh water for this purpose.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Thu 19 May 2011, 11:38:29

In a way, this is similar to a hydroelectric dam. In a dam, we use a large wall like structure to stop the flow of water to let the potential energy build-up. Then we let the water out of small outlet and use the intense pressure of flowing water to generate electricity. In effect we are focusing the energy of the flowing water at a small point. We can do the same with sunlight too, we have to make the process cheaper by using readily available materials and simple design.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby pstarr » Thu 19 May 2011, 11:41:01

how do you track the sun?
edit: okay I read that the sterling engine and small lens move. So instead of moving a heavy parabolic dish you are moving a heavy sterling engine. Where is the efficiency gain?
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Thu 19 May 2011, 22:28:03

I suspect this design will be less efficient than the Stirling dish systems. But why is efficiency so important? Sunlight is free. Would you care about the mileage of your car if gasoline was free. The problem is the development cost. The materials that are currently used for capturing solar thermal energy are very expensive. Plus i do believe that moving just the sterling engine along a rail-like arc instead of moving the entire dish over a heliostat pole would be cheaper.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Sat 21 May 2011, 02:37:50

If you want to concentrate sunlight using cheap lenses on a stationary stirling engine here is a solar thermal collector design that can be used:-
http://openfarmtech.org/forum/discussion/134/another-design-for-a-cheap-solar-thermal-collector

The system shown in the image below can be used as a concentrating solar thermal system. The object is to achieve a concentration ration of 100:1 using as little expensive materials as possible.

http://www.freeimagehosting.net/image.php?b8ee3f6d70.jpg


• It uses an array of transparent plastic or glass spherical containers that act like a spot lenses when filled with water. Each lens focuses a small amount of sunlight at its own focus with a concentration ratio of 10:1.

• The focus of this lens would be a small spot, just like a parabolic dish. We have to place a very small dual-axis adjustable mirror controlled by a microprocessor at this focus.
• An array of such collectors would be used to focus light at another single spot. The effective concentration ratio at this point depends on how many lenses we are able to place in an array.

• Since the focus lies below the lens, one needs to take care that the lens is placed at a sufficient elevation so that there is enough room for the mirrors to move throughout the day and still focus light at the same spot.

• This system acts as a cheaper alternative to expensive dish-sterling systems.

The mirror associated with each lens will have to move along an arc throughout the day as the focus of the lens shifts with the moving sun. It will also have to be adjusted to keep reflecting the on a fixed spot. No big deal for modern microprocessors.


Advantages of the lens collector over the Dish Collector:-

• It does not eliminate the need for reflective glass surface completely. But this design will significantly reduce total surface area of expensive glass required, thus reducing the the cost of construction.

• In the Dish collector, it is required that the entire dish has to track the movement of the sun continuously. This requires giant heliostats. But in the lens collector, only the small mirror at the focus has to be adjusted according to the movement of the sun. It requires cheap microprocessors and small motors that can be programmed easily.

• The round shape of the heavy lenses provide better protection against strong winds than the large dish shape.

• With clever design and engineering, I am sure that several lenses can be placed in an array to provide a significantly high concentration ratio.

• Small mirrors and the microprocessor control system would be cheaper. The cost of microprocessors have been falling steadily in recent years.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby efarmer » Sat 21 May 2011, 09:50:58

Count me in, I have always been a huge fan of magnificent jugs glistening in the sunshine.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby PrestonSturges » Sat 21 May 2011, 13:37:08

efarmer wrote:Count me in, I have always been a huge fan of magnificent jugs glistening in the sunshine.


http://www.kindgirls.com/gallery/erroti ... 37545/3232

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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Mon 23 May 2011, 03:44:12

How much would a 1 kilo-watt stirling engine with hydrogen as working fluid cost? What temperature would be required to operate it?
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Thu 30 Jun 2011, 21:15:20

Here is a video showing a guy using a glass ball for focusing sunlight for cutting.

http://www.markuskayser.com/work/sun-cutter/

I propose to use a similar transparent ball, only larger. A large plastic ball filled with water should be able to focus enough sunlight to drive a Stirling engine or boil water.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby Shaved Monkey » Fri 01 Jul 2011, 01:03:19

There was talk of building a solar wind farm in Australia a few years ago.
The idea was a big glass house with a central chimney.
Hot air rose up the chimney turning a turbine
The surrounding glass house was rented out to grow food.
They havent been able to get the funding to do it so it hasnt happened.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby prajeshbhat » Fri 01 Jul 2011, 01:10:09

That's the solar updraft tower. There used to be a prototype in Spain in the 80's. It had a plastic canopy. It generated 50 KW. Worked for 3 years. Cost about a million dollars. The main problem with this design was its extremely low conversion efficiency(0.5%). If you want a reasonable conversion efficiency (10% or more), you have to focus sunlight. The trick is to use the cheapest possible materials. I want to use plastic and water.
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Re: Simple Design for a Cheap Solar Thermal Collector

Unread postby spot5050 » Fri 01 Jul 2011, 20:07:02

Wow. Next time I want to melt a bin liner or set fire to a leaf, I will give you a call.
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Re: Dismantling old solar water heater

Unread postby papa moose » Fri 29 Jul 2011, 00:58:31

Linda27 wrote:Solar water heaters are not the version of the tankless water heater solar. The solar aspect of the title has to do with how the water is heated. There are two parts to this system: the solar collectors and storage tank. Solar collectors are equipped with a special enamel coating the walls of the box or components or conduits through collectors containing a heat transfer fluid, which is also useful in climates where residents and businesses find temperature is often below freezing in the winter months.

solar hot water perth


Linda,
Thank you for registering just to answer my enquiry.
I actually did pull these units off the roof a few months back, angle grinder and drill to partially dismantle each unit then a quick heft off the roof to land them on the back lawn (apart from the glass sheets, they were a bit tricky but got down ok in the end).

The units were sheet metal boxes with a glass lid, the interior of each box was lined with fibreglass batts, directly below the glass was a sheet of copper and 1/2" copper tube zigzagged backwards and forwards from one side of the box to the other. It was simple mains water going thru the tube, if there was ever a ground level storage tank (probably was) it is long gone before i bought the house.

Thanks to all for your responses.
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Solar Thermal: Deep Blue NRG Group

Unread postby conrad1ke » Sun 15 Dec 2013, 23:32:52

Solar thermal systems pose some of the most promising renewable alternatives to traditional natural gas and electrical fuel sources. For residential applications, these systems are capable of providing 100% of the domestic hot water load, with excess energy routed to pool heating or space heating applications. Typically, these systems are used to offset between 50-90% of the incumbent water heating fuel source, depending on your latitude. The result is a super-efficient water heating system. For example, your incumbent 65%-efficient water heater, supplemented with a solar thermal system that provides a mere 60% of the load offset, would suddenly become over 150% efficient.

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http://deepbluenrg.ca/applications/solar-thermal/
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