Solar collector made from plastic bottles: a step-by-step guide to assembling a solar device

The concept of alternative energy for many owners of private houses and summer cottages is associated with expensive solar panels, wind turbines or heat pumps. No one even realizes that in just a few hours, for mere pennies, you can build a solar collector from plastic bottles to supply yourself with hot water throughout the warm season.

We will tell you how to make an effective sanitary water treatment system from waste materials. In our article you will find a detailed description of the designs and methods of manufacturing systems, the operation of which has been tested in practice. Taking into account our recommendations, you will assemble a useful household device without any hassle.

Specifics of using solar collectors

The main difference between a solar collector and various types of heat generating solar systems consists of cyclical work. In other words, in the absence of the sun there will be no thermal energy.

Obviously, in the dark, the performance of an autonomous hot water system with a solar collector is reduced to zero. Heat production by a solar collector is determined by the length of daylight hours, which depends on latitude and time of year.

A homemade solar collector will solve not only the issue of supplying hot water to a house not connected to central networks, but also heating problems

The climatic features of the area also have a significant impact on the performance level of the solar collector. If the area is characterized by frequent fogs or the sun is often hidden behind clouds, then the performance of the solar collector is significantly reduced.

However, in this case too solar collector for heating and/or water heating remains effective due to its ability to capture even scattered rays.

Design features and principle of operation

The main element of the standard version of the solar collector is an adsorber in the form of a copper plate with a tube. The plate quickly heats up under the influence of sunlight, transferring heat to the tube and the liquid in it. Thanks to free or forced circulation, the resulting heat is further transported throughout the system.

Under the influence of sunlight, the copper plate is heated, from which heat is transferred to the coolant located in the tube

To increase the efficiency of the adsorber, it should be endowed with the necessary physical properties. First of all, it is necessary to increase the absorption capacity of the adsorber and minimize the reflection of sunlight. The simplest solution would be to apply black paint to the adsorber.

To increase the efficiency of the adsorber, it must be covered with transparent glass. Ordinary glass reflects some of the sun's rays.

It is best to use special glass with a low iron content or use an anti-reflective coating. To avoid contamination of the glass, the body of the solar collector should be made airtight.

Despite the many ways to improve the operation and increase the productivity of a solar collector, due to imperfections in the design, this indicator is far from ideal. Taking into account the principle of operation of a solar collector and methods for increasing its efficiency, we will try to create a primitive and inexpensive model from scrap materials.

Assembling the unit from scrap materials

In addition to being cheap and easy to assemble, the option made from plastic bottles differs from standard solar devices in that flat solar collectors do not work well in the morning and evening hours.

The convex shape of the bottles ensures almost vertical penetration of rays even during sunset and dawn, thereby ensuring the efficiency of the device both in the morning and in the evening.

Thanks to the convex shape of plastic bottles, the device, even in a horizontal position, is able to capture the rays of the rising and setting sun

There are several distinctive ways to construct a perfectly working hot water system from plastic bottles:

• The solar collector plays the role of a storage tank in which water is heated and then drained;
• The solar collector is connected to a storage tank to ensure water heating and natural circulation;
• Plastic collector bottles act as a water reservoir;
• Plastic bottles act as sealed containers to retain heat.

Also, solar collectors may differ in their design features. First of all, this is due to both the method of fastening the bottles and the methods of their location.

Option with heated water storage

To make a solar collector you will need polypropylene pipe with a diameter of 50 mm, to which plastic bottles will be connected, the number of which is determined by the diameter of the pipe. For the template, 15 plastic bottles were taken, so the working capacity of the solar collector was 30 liters.

The joints connecting the bottles to the propylene pipe are coated with silicone sealant, preventing water leakage

To connect the bottles into a single system, holes must be drilled in a propylene pipe intended for hot water supply. The ideal solution was to use a 26mm wood drill bit.

With these dimensions, maximum joint density is ensured, and the bottle is screwed into the hole with force along its thread. To ensure maximum sealing of the connection, the joints can be coated with silicone sealant, but it is better to use hot melt adhesive.

To achieve the effect of communicating vessels, holes with a diameter of about 2 mm must be made in the upper part of each bottle.

After connecting the bottles, a fitting is cut into one side of the pipe, which will later be connected to the water supply for water supply. On the other side, you should install a tap through which the heated water will drain into the storage tank.

However, under the weight of the filled water, such a device for household use solar energy may lose its integrity. Therefore, it would be advisable to install a box. To make it you will need a board 150 mm wide.

To increase the efficiency of the solar collector, you can lay foam plastic or polystyrene foam 50 mm thick on the bottom of the box and cover it with foil.

After installing the solar collector at the place of its further use, plastic bottles must be painted black to more effectively absorb sunlight.

When painted black, the absorption capacity of the plastic increases and the efficiency of heating water increases.

It is better to use matte paint and apply it by spraying from an aerosol can. All that remains is to cover the box with glass, thereby increasing its tightness and connect it to the cold water supply system and the system for draining warm water prepared for use into the storage tank.

From practical experience it is known that plastic does not tolerate high temperatures, which lead to its deformation. On bright sunny days, the temperature of the heated water can exceed 65 degrees, which will lead to deformation of the plastic.

In this regard, it is better to refuse additional sealing of the box with glass at all or to use it exclusively in cloudy weather.

Method with circulation of heated water

The solar collector system is similar to the first option, but has a number of design differences.

To create a collector you will need the following tools and materials:

• PVC pipe with a diameter of 20 mm with corners and tees;
• Roller pipe cutter;
• Chamfer cutters;
• Primer (cleaning agent);
• Plastic bottles;
• Tetrapacks for milk or juice;
• Stationery knife;
• Cardboard;
• Heat-resistant matte black paint;
• Storage tank.

For installation we will need a PVC pipe with a diameter of 20 mm. The horizontal part of the pipe should be cut into sections into which angles and tees will be attached by cold welding.The bottom of the solar collector will look exactly the same. The end result is a closed system, but first things first.

Features of gluing PVC pipes

To obtain a high-quality cut, it is better to use pipe cutterequipped with rollers. After cutting, the inside of the pipe must be chamfered using special chamfer cutters.

After measuring the depth of the tees and angles, you need to place a mark on the end of the pipe being connected and treat the ends of the pipes and fittings with a primer (cleaning agent).

Thanks to the smooth movement of the cutting part, the roller pipe cutter allows you to avoid cross-section deformations and the formation of burrs along the edge when cutting

The next step is to apply and spread the glue around the outside of the pipe and the inside of the fitting. The glue must be applied with a brush, and its size should be smaller than the diameter of the pipes. All that remains is to insert the pipe into the prepared tee or corner and turn it a quarter turn to evenly distribute the glue.

It should be taken into account that the work of gluing one corner or tee should be completed in no longer than 30 seconds. After fixing, it is necessary to remove any remaining adhesive.

The procedure for manufacturing a solar collector

After preparing the top pipe and attaching the vertical pipes to it, you can begin preparing the plastic bottles. The presented solar collector model has 4 vertical pipes 105 cm long; this length of pipe can accommodate 5 plastic bottles. That is, to assemble the collector you will need 20 identical plastic bottles.

The bottom must be removed from each bottle. To do this, make a simple template from a 30 cm long piece of cardboard rolled into a tube.Using a template and a utility knife, remove the bottom of the bottles. After preparing the bottles, you can begin making an absorber that will absorb solar energy.

Using a simple cardboard template allows you to quickly cut and get bottles of the same size

We use used juice or milk tetra packs as an absorber. They must be cut, thoroughly washed and dried. To improve their absorption capacity, apply matte black paint. The easiest way to do this is to use spray paint from a can.

Sequential stringing of plastic bottles makes it easy to place folded tetra packs in them

After preparing the bottles and tetrapacks, you can begin assembling the solar device. First, you need to string a plastic bottle, neck first, onto a vertical tube and insert a Tetra Pak into it. In a similar way, all the bottles are strung on vertical tubes, which then must be connected to the tees and corners of the lower pipe, similar to the upper one.

To give rigidity to the manufactured solar collector, it is necessary to make a support for it.

An ordinary wooden panel gives rigidity to the structure and makes it easy to move the solar collector to the place of its operation

You can, as in the first case, place the collector in a wooden box, but there is no longer any need to insulate it. Since each of the plastic bottles is a kind of small insulated reservoir, which, heating up from the inside, transfers heat to the water circulating through the tubes.

Features of placement and connection

For maximum possible absorption of sunlight, the collector must be oriented in a southerly direction. A small tilt angle of 10-15 degrees is enough for the collector to work effectively in almost any position of the sun.

The lower part of the pipe must be connected to the bottom of the storage tank, and the upper part - approximately to its central part. Cold water from the polymer container will flow through the lower pipe into the collector, where it will heat up and rise through the upper tube into the tank.

Thus, there will be natural circulation of water through the homemade system. To ensure high intensity of water circulation, the tank should be placed just above the solar collector at a distance of at least 0.3 m from it.

When the solar collector is correctly connected to the storage tank, natural circulation of water is ensured

It should be taken into account that when cold water enters the tank from the water supply system, it is actively mixed, which reduces the efficiency of the collector. This can be avoided by equipping the inlet to the tank with a turbulent reducer, which is a plugged tube with multiple holes.

Water flows smoothly through the reducer, which allows cold water to remain in the lower layers, from where it is taken into the solar collector.

The use of a turbulent reducer helps to avoid mixing cold and warm water in the storage tank

Obviously, the solar collector provides water heating only during the daytime in sunny weather. Therefore, it is important to save hot water for use during the day and evening. To do this, it is necessary to insulate the storage tank.

Conclusions and useful video on the topic

Video 1. This is how the first solar systems from plastic bottles appeared:

Video 2. Almost free water heating device in action:

A solar collector made from plastic drink containers is a cheap solution for producing hot water. However, in case of prolonged bad weather, especially in spring and autumn, it is advisable to install a heating element in the storage tank. In this case, the solar collector will become part of a complete system, allowing, under favorable conditions, to save money.

Tell us about your experience in building a homemade solar system from plastic bottles. It is possible that you have information and design options in your arsenal that may be useful to site visitors. Please write comments in the block form below, ask questions, share photos and useful information.