Solar heater with recyclables

The solar heater made from recycled materials is a sustainable and economical alternative for heating water using resources that would normally be discarded. This project, developed by José Alcino Alano and his family, aims to save energy and preserve the environment, highlighting the importance of recycling in everyday use. This guide will provide the necessary information for the construction and installation of a solar heater made from PET bottles and Tetra Pak boxes, promoting environmental awareness and the reuse of materials.

Origin and Objective of the Project

The solar heater project was born from the need to find a useful destination for recyclable packaging, in line with the environmental concern of adopting environmentally friendly systems whenever possible. The simplicity and low cost of this system allowed it to be widely implemented in several institutions and low-income homes, with the aim of saving electricity and reducing environmental impact. In addition to its practical function, the project also seeks to raise awareness among the population about the potential of post-consumer materials, which can have useful applications in the social and environmental aspects.

Although the focus of this manual is the construction of a solar heater with recyclable materials, it is important to mention that there are other solar heater systems on the market, which may be a viable option for those with greater purchasing power.

Solar Heater Operating Principles

The solar heater basically works through two systems: thermosiphon circulation and forced circulation. Both are efficient methods for heating water using solar energy, but they differ in their application and complexity.

Siphon Thermo Circulation

This is the simplest and most ideal method for low-cost solar heating systems. It works based on the difference in density between hot and cold water. Cold water, being heavier, pushes the hot water upwards, causing it to circulate through the system. For this process to work correctly, it is crucial that the solar collector is installed in a position lower than the bottom of the water tank or reservoir, thus ensuring that the water circulates naturally while there is solar radiation. This principle is similar to that used in conventional solar heaters, with the difference that, in the case of the recyclable solar heater, the materials used are much more accessible and sustainable.

Forced Circulation

In the forced circulation system, the solar collector is installed in a higher position than the tank or reservoir. This method is commonly used to heat swimming pools. Here, a thermosensor activates a motor pump when the water temperature in the collector reaches a predetermined level. This allows the hot water to be exchanged for cold water efficiently. However, to prevent the system from working in reverse at night or during periods of no sunlight, it is necessary to install a check valve. This system is more complex and requires a larger investment, but it offers greater control over the heating process.

Construction of Solar Heater Components

The construction of a solar heater requires careful preparation of its components, especially the solar collector, which is responsible for the efficient performance of the system. This project stands out for using recyclable materials such as PVC pipes, PET bottles and Tetra Pak boxes, replacing conventional materials such as copper, aluminum and glass.

Solar Collector Construction

The solar collector is the most important part of the system, being directly responsible for heating the water. In this project, the heat absorption columns are made of PVC pipes, which are less efficient than copper or aluminum pipes, but serve the purpose of reducing costs. PET bottles and Tetra Pak boxes replace the heat absorption panel and glass used in conventional collectors. The Tetra Pak boxes, painted matte black, absorb the heat, which is then retained inside the PET bottles and transferred to the water in the PVC pipes.

Special attention must be paid to the sizing of the solar collector in relation to the water tank or reservoir, to ensure that the water temperature does not exceed 55ºC, thus avoiding softening of the PVC pipes and possible leaks.

Selection and Preparation of PET Bottles

The choice of PET bottles is crucial to the success of the project. It is recommended to use transparent and smooth bottles (crystal type), preferably from the Coca-Cola and Pepsi brands. Although some green bottles are being tested with similar results, the use of crystal bottles is safer to ensure the durability and efficiency of the solar collector.

To prepare the bottles, it is suggested that after drinking the soda, they be washed and left to drain. A useful trick is to place them in the refrigerator for two minutes without the cap and then quickly cap them, which prevents them from getting crushed when stored for future use. If some bottles are crushed, they can be recovered by heating them in the microwave with a little water, following the necessary safety precautions.

Preparation of Tetra Pak Boxes

The Tetra Pak boxes used in the project are made of aluminum, polyethylene and cellulose, making them ideal for withstanding the internal temperatures of the solar collector. To prepare them, the boxes must be opened, washed and cut to a standard size of 22.5 cm in length. After being folded and painted matte black, the Tetra Pak boxes are inserted inside the PET bottles, where they act as the main heat-absorbing element.

Solar Heater Installation

Installing a solar heater requires specific care to ensure the efficiency of the system and the safety of users. The main aspects of the installation are highlighted below:

Project Sizing

Proper sizing of the project is essential for the solar heater to function properly. It is important to take into account water consumption and the region of the country, as these factors directly influence the efficiency of the system. In colder regions, for example, it may be necessary to increase the size of the solar collector to compensate for the lower incidence of solar radiation.

Fixing Brackets and Thermal Insulation

The mounting brackets for the collector and water tank must be robust enough to support the weight of the system, especially when full of water. In addition, thermal insulation of the pipes connecting the collector to the water tank is crucial to minimize heat loss and ensure that the water arrives hot at the point of use.

Mixer Distance and Installation

The distance between the solar collector and the water tank should not exceed 3 meters, to ensure that the water circulates efficiently. In addition, it is recommended to install a hot and cold water mixer, which allows you to adjust the water temperature as needed. This installation is simple but practical, and contributes to the comfort of users.

Summary and step by step

Step by Step in Building a Solar Collector

1. Selection of PET Bottles and Cuts:
   • Use three types of PET bottles: smooth transparent (straight) ones, curved ones from Coca-Cola and Pepsi, and some green bottles.
   • To cut the bottles accurately, use a simple jig. Cut two pieces of 100mm PVC pipe: one 29cm long and the other 31cm long. Cut the pipes lengthwise so that the bottles can fit through. Use the 29cm pipe for plain and Pepsi bottles, and the 31cm pipe for Coke bottles.
   • After cutting the bottles, wash them, let them dry and store them properly to avoid deformation.
2. Preparation of Tetra Pak Boxes:
   • Use 1 liter Tetra Pak boxes (milk, juice, etc.).
   • Wash the cartons, let them dry, and cut them to 9" (22.5 cm) lengths. Make an additional 3" (7 cm) cut at the bottom to fit the neck of the next bottle.
   • Bend the Tetra Pak boxes so that they fit the inner curvature of the bottles. Then, paint them with black synthetic enamel paint.
3. Solar Collector Assembly:
   • Insert the painted Tetra Pak boxes into the cut bottles, ensuring they are well positioned to maximize heat absorption.
   • Place the bottles in black painted PVC tubes, which will serve as heat absorption columns.
   • Make sure the bottles are securely fastened and there are no gaps between them to prevent heat loss.
4. Installation and Positioning:
   • Install the solar collector in a location with good exposure to the sun, preferably with the upper bar of the collector connected to the hot water return, below the level of the water tank.
   • Ensure that the difference in height between the collector and the water tank does not exceed 3 meters to ensure efficient water circulation.
5. Testing and Final Adjustments:
   • After installation, test the system to verify that the water circulation is working correctly.
   • Make adjustments as necessary to ensure the system reaches the desired temperature without compromising the integrity of the materials.

Benefits of Solar Heaters for the Environment

The adoption of solar heaters, especially those made from recyclable materials, brings significant benefits to the environment. By reusing PET bottles and Tetra Pak boxes, we reduce the amount of waste disposed of and decrease the demand for new natural resources. In addition, the energy savings promoted by these systems contribute to the reduction of greenhouse gas emissions, helping to combat climate change.

The use of solar heaters also represents significant savings on energy bills, especially in regions with high incidence of solar radiation. This makes investing in solar heaters not only an environmentally responsible option, but also an economically viable one.

The solar heater made from recyclable materials is a simple, affordable and effective solution for heating water. In addition to promoting energy savings and benefiting the environment, this project stands out for its ease of implementation, using materials that are often discarded without being used. With proper planning and correct installation, it is possible to enjoy hot water in a sustainable way, contributing to a greener and more conscious future.

Finally, it is important to remember that, although the project is simple, special care must be taken during the construction and installation of the system, especially when handling recyclable materials to avoid contamination. With creativity and good will, this project can be adapted to each person's needs, promoting the conscious use of solar energy and the reuse of materials in favor of the environment.

Check out other interesting facts about recycling clicking here.
Learn how to make art by recycling, Click here.