Summer shower with solar collector. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Summer shower with solar collector. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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The article discusses the design and manufacturing technique of a summer shower with a solar collector. The installation is designed for home production and the use of widely available materials only. The article is intended for the happy owners of their own houses and cottages who have not lost interest in technical creativity.

Thinking along the tree

As soon as I had my own house, a young technician immediately woke up in my soul, and the magazines of the 60s with the same name with a mass of extremely useful and interesting designs, where there was a conversation about the use of solar energy, surfaced in my memory. But, as we usually do, any resettlement begins with a major renovation, and my case is no exception. Working on the roof on a fine summer day is very conducive to thinking about the possibilities of using so much orphan energy. And I got the final impetus to the manufacture of this design by sitting on a large black shoe knife, which had lain in the sun for a couple of hours.

Speaking seriously, the use of solar energy could give quite tangible savings in electricity and gas (at least in our region - the south of Ukraine). There is no downward trend in energy prices, so it makes sense to think about savings in advance. In the fall, after the building fever subsided, I decided to take this issue more seriously. As it turned out, quite a lot of literature on this issue is available online [1], [2], [3]. Having carefully studied everything that I managed to get, I came to the conclusion that it is most efficient and technically simple to implement water heating in a boiler with its inclusion in the general hot water supply system at home. Options associated with significant structural alterations of the building were immediately discarded, and the use of photovoltaic converters was too expensive and less efficient. After carrying out preliminary calculations, it turned out that it would be a rather grandiose structure. In addition, a lot of technical issues related to the manufacture of a solar collector immediately arose. The books say a lot about what to do, but not how. Therefore, I decided to practice on the "cats" and build an outdoor shower to start with to check the correctness of the calculations and design options.

The work of the shower was planned in the "impulse" mode - heating during the day, and in the evening - friendly splashing of the whole family under the shower. Estimating the required dimensions of the collector, I proceeded from the fact that the temperature of the water in the water supply (during the warm season) is 15-20°C, and the desired temperature in the boiler is about 40°C. Therefore, it was necessary to raise the temperature of 60-80 liters of water by 20-25°C. The calculation turned out to be very approximate, since when delving into the calculation methodology, it turned out that there are a lot of approximate coefficients (I am not an expert in the field of heat engineering, and the "tail sense" in this area has not yet developed). As a result, I got the required collector area in the region of 0,5-0,7 m2. Guided by book wisdom, the laws of physics and common sense, I set about designing.

solar collector

As a matter of fact, this is the main element of the solar installation and the main headache. After getting acquainted with the prices for factory products, I immediately lost interest in them, I decided to make it myself. I wanted to make the collector simpler, cheaper, better and without the use of machine tools and carbon dioxide welding. At first I toyed with the idea of using a stamped flat heat sink (gleaned from one of the books), but as it turned out, they have not been produced for a long time. In my search, I moved to a flea market, I didn’t find them there either, but I stumbled upon a magnificent aluminum barrel - narrow and tall, resembling a giant finger (of course I bought it). I did not want to assemble a heating panel on a thread from water pipes and tees - both a lot of weight, and low corrosion resistance, and a significant increase in hydraulic resistance due to the large number of tees with sharp jumps in the flow area. In general, a gloomy shadow hung over the idea.

The problem was solved when I wandered into a plumbing store and saw a copper pipe for heating systems. It was what we needed - high corrosion resistance, ease of assembly (soldering), reasonably made fittings - with virtually no jumps in the flow area. Once you visit a good shop, you will get 90% of the necessary materials for the entire solar plant.

The design of the solar collector shown in fig. 1. The pipes of the cold and hot water hydraulic manifolds are made of 18mm pipe sections and tees, the heating pipes are 15mm in diameter. To connect to the system, 3/4" thread adapters are used, the other two ends are plugged. A 0.8mm thick steel sheet is soldered to the heating tubes. It took 20 tees, 5 meters of a pipe with a diameter of 15mm, 1,5 meters of a pipe with a diameter of 18 mm to manufacture the solar collector , two plugs and two adapters.In addition to these materials, you will need a roller pipe cutter, solder with flux and the cheapest gas burner, all this is purchased at the same plumbing store.

Fig.1 (click to enlarge)

The production of the heating panel begins with cutting the required number of tubes, after that the first heating tube and intermediate tubes are soldered into two tees, then the next two tees with an inserted (but not soldered) heating tube are put on the intermediate tubes, and all connections are soldered, and so on. Lastly, plugs and adapters are soldered. The assembly should be carried out on a flat plane, that is, after installing the next pair of tees, the entire structure should be laid on a plane and leveled, and then soldered (it is better to solder directly on the plane if it can withstand it). Soldering is carried out as follows: a thin layer of flux-solder 10-15 mm wide is applied to the end of the pipe, the pipe is inserted into the tee (coupling) and the solder point is heated with a burner until the solder melts.

After that, a metal sheet is soldered to the heating tubes, this is the most difficult and unpleasant part of the work. Firstly, you should stock up on a sufficient amount of ordinary solder, and secondly, by placing the heat exchanger on the sheet, you should mark the places where the heating tubes pass and irradiate them. It is convenient to solder by placing the entire structure at an angle and simultaneously using a powerful (90 watt) soldering iron and a gas burner. Before soldering, the sheet must be pressed against the tubes, I used several clamps, rearranging them as needed. You can drill holes in the sheet with a diameter of 1-1,5 mm and pull them with wire. The tubes must be soldered along the entire length on both sides, sparing no solder. After soldering is completed, hydraulic tests should be carried out, for example, by plugging one outlet and connecting the other to the water supply. Nowhere and nothing should flow and drip. The finished heating panel is painted with a black matte heat-resistant paint in two layers, the paint is sold in an aerosol can at any hardware store. Lastly, tee 10 and transition 1 are installed.

The finished panel is placed in a wooden box (Fig. 2). The box is assembled into a spike from four boards 25 mm thick. Before assembling along the long sides of the boards on both sides, a groove 6 mm deep and 6-8 mm wide is selected with a planer. To increase the rigidity of the box flush with the bottom edge of the grooves, wooden bars 30x30 mm are glued into the corners of the box, two of the same bars 300-400 mm long are glued (approximately in the center) from the inside along the long side of the box from the side of the back cover installation. They serve to fasten the back cover of the box, made from a piece of plywood 6 mm thick.

Fig.2 (click to enlarge)

For the passage of the inlet and outlet pipes, grooves are cut out in the box. It is better to do this in place, fixing the pre-heating panel. For gluing the box, you should use a good waterproof glue, "Liquid nails" are quite suitable. After manufacturing and fitting all parts of the box, they were impregnated with a water-repellent composition (trade name "Polyfluid") and painted with synthetic enamel twice.

The collector is assembled in the following order:

On the back cover, four wooden spacers 50 mm thick are fastened with screws (care should be taken that the spacer does not fall under the heating tube).
A layer of glass wool is laid on the lid with an allowance of 90-100 mm, opposite the spacers, the glass wool is pushed apart.
Install the heating panel on the spacers, and fasten it to them with screws.
Insert the back cover into the box, and fasten the cover with screws to the bars.
Straighten the glass wool along the walls of the box, and fix it in several places with thin nails with wide washers.
Install a protective glass on silicone sealant.
Blow out the passage of pipes with construction foam.

The equivalent heating area of the solar collector is ~0,5 m2.

Assembling the solar plant

The complete scheme of the solar plant is shown in Figure 3. The solar plant is single-circuit, thermosyphon type and is designed for permanent connection to the supply water main. Such a scheme has been described many times, and I will not repeat myself, but will focus on its technical implementation.

I have already mentioned the storage tank, this is an aluminum barrel, which, after alteration, has a capacity of approximately 0,3 m2. Initially, the capacity of the barrel was about 0,5 m2, it seemed to me a little too much and, shedding tears, reduced its height by 0,8 m. For thermal insulation, the tank was wrapped in two layers of mineral wool 50 mm thick. Two layers of waterproofing fabric are laid on top of the cotton wool, the fabric is fixed with a thin knitting wire. A circle of roofing material (in the form of a skirt) is placed on top and is also fixed with a knitting wire. Of course, an aluminum barrel is a luxury (just lucky), a steel container painted on the inside with waterproof paint is also quite suitable. You can also try a plastic container, but with a constant stay on the street, their durability is not very great. The general requirement for any type of tank is that it should be narrow and tall.

The fittings in the tank are made of galvanized spurs 100-150mm long. To connect the solar collector, 3/4" sleeves are used, for the feed water supply fitting - 1/2". The fitting design is shown in Figure 4. Here the only possible problem may be large diameter washers. There were no such stores, I found suitable ones at a flea market. The holes in the tank are first drilled, and then brought to the required diameter with a file.

Fig.4 (click to enlarge)

The pipelines are made of a metal-plastic pipe, working with it does not cause any problems and no special tool is required (by the way, it can be perfectly cut with a roller pipe cutter). With large bending radii, you can do without a bending spring. Another of its positive properties: low hydraulic resistance. For thermal insulation of pipes, a standard heat-insulating sleeve is used (purchased in the same place as the pipe).

A float valve from the toilet cistern is used as an automatic supply water valve. When choosing a valve, you should not save money - firstly, the valve must be reliable so as not to climb up every week and, secondly, when it is opened, water should flow mainly from the outlet, and not fly in all directions. A plastic tube is put on the outlet pipe of the valve, reaching to the bottom of the tank. When water is withdrawn, cold water enters the bottom of the tank and displaces hot water to the top.

The outlet pipe is made of a piece of galvanized pipe with a 1/2" thread cut at one end, 150 mm long. The pipe is sealed in the bottom of the tank in the same way as the fittings are sealed, a standard ball valve (preferably with a long handle) is screwed onto the remaining end of the thread. Accordingly, the valve a watering can is screwed in. Apparently, the best solution would be to use a floating water intake and take water from the upper layers. But I did not find a sufficiently flexible and reliable tube, and I did not want to change the tube every season. During the operation of the solar plant, it turned out that on a hot day the temperature water level is too high for washing, the outlet has been slightly modified, a tee has been installed between the outlet and the valve, and colder water is supplied through a flexible hose and a faucet to it from an additional fitting installed in the bottom of the tank.

The solar collector is installed at an angle of 45° and is directed exactly to the south. A general view of the solar plant is shown in Figure 5.

Summer shower with solar collector
Ris.5

The design of the shower stall is arbitrary, but it must withstand the total weight of a full tank and yours. I welded the frame of the booth from a pipe with a diameter of 40 mm and a 40x40 square, the floor and roof are made of boards 40 mm thick. The design has a significant excess margin of safety, but I have further views on the prospects for its use.

I want to note that the dimensions indicated in Figure 5 are not a dogma and are advisory in nature. For the system to work well, three main conditions must be met:

ensure good thermal insulation of all parts of the installation,
provide minimum hydraulic resistance,
ensure the maximum height difference between the inlet pipe of the solar collector (12) and the hot water connection (9) installed on the tank.

The results

The installation has been in operation for two seasons, no problems have arisen and no maintenance has been required (naturally, in autumn the water is drained and all taps open, and the reverse operation is performed in spring). The indirectly calculated efficiency of the installation is about 0,38 (it is planned to carry out more accurate measurements for the solar collector). After filling the installation with water or after prolonged rains, the installation enters the mode for several days. The shower can be used from May to October. In spring and autumn, the water temperature, in the area of the outlet, ranges from 25 to 30°C. A certain mistake came out with the booth, I made it too open, and although the water is quite warm, the air is cold in the evenings, I recommend taking it into account. In the summer months, with partly cloudy (possible with a short rain), the water temperature is 34-37°C, on hot days it reaches 42-45°C. The amount of hot water is enough for 3-4 people to wash normally (sometimes friends test).

Gas consumption in the summer has noticeably decreased, the gas column is practically not used, gas consumption does not exceed 4-5 m3 per month. In general, the task was solved satisfactorily - for the manufacture of the solar installation, only purchased widely used materials were used, no machine work was required, we were provided with hot water for washing (free of charge) all summer. I am satisfied with the results, received a positive impetus for further work towards the use of free natural energy, and I am terribly proud of what I have done.

Literature

1. Sabadi P.R. Sunny House, Moscow: Stroyizdat, 1981.
2. Systems of solar heat and cold supply, ed. Sarnatsky E.V., Chistovich S.A., Moscow: Stroyizdat, 1990.
3. N. V. Kharchenko, Individual solar installations.
4. Artyushenko N.M., Heating of individual houses, K: Budivelnik, 1980.

Author: Evgeny Karpov

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