Greenhouse Heating with Solar Energy

Our Colleague, Mustafa Özenç has been studying on green and sustainable energy sources in order to protect our world. You may find below his article regarding solar energy for greenhouse heating;

Today, greenhouse cultivation has a great importance in the agricultural field. One of the biggest advantages of greenhouse cultivation is the possibility of yielding fruit and vegetables in summer and winter. Thanks to a parabolic increase, greenhouse has a great importance in Turkey and also the world. As in all aquaculture, paying attention to some situations in greenhouse cultivation increases the yield and quality of the products grown in the greenhouse. We can think of these situations as the choice of location, whether the greenhouse is plastic or glass, which fruit or vegetable will be grown, the optimum temperature to be provided, and so on. Greenhouse heating is one of the main things that should be done in order to get efficient harvest in summer and winter. In recent years, various methods have been used in greenhouse heating. These methods can be listed as follows;

1. Heating with stoves,

2. Heating with radiator,

3. Hot air heating,

4. Electric heating,

5. Heating using waste energy.

6. Heating by using natural energy sources (Solar energy)

The reasons such as the low initial investment cost, the availability of fuel and the availability of the necessary labor force, make heating the stove heating methods the most used method in our country in terms of greenhouse heating.

Heating system with radiator is the least used heating method in our country because the initial construction and operating costs are high. It is not recommended to be applied in greenhouses smaller than 2.5 decares.

One of the natural energy source that can be used in greenhouse heating is geothermal energy. In some regions of our country that contain a hot water source, hot water was extracted by drilling to the surface and greenhouse heating was provided after the necessary system was installed, but some problems made it difficult to use this method.

Electrical heating systems have low initial construction costs and automatic control of the systems. In contrast, the operating costs of electrical heating systems are quite high. Therefore, this method is not widely used in practice.

It is possible to use waste energy from various factories for heating in greenhouses. Especially hot waste flue gases and cooling water can be used for this purpose. This method can be counted among the new methods which are not in use in our country.

Greenhouse heating method, which takes advantage of solar energy, has gained importance in recent years; the increase in fuel costs and electricity charges, and the inability to sell the products to the desired prices, has pushed greenhouse owners to a compulsory saving. The use of solar energy in heating methods, which has the most important share in operating costs, has gained great importance. For this purpose, solar energy is used passively and actively in the heating of greenhouses with solar energy.

In passive use, it can make good use of solar energy by directing the greenhouses and regulating the roof slope accordingly. For this reason, the length of the greenhouses should be regulated towards 10 ° east from the south under the conditions of our country. Thus, the utilization rate of solar energy can be increased. This type of roof arrangement requires more construction material as well as good workmanship. . In the solar greenhouse implemented in İzmir, the basic principle is that the northern wall of the greenhouse is constructed as an energy collector and storage heat wall. Solar energy is converted to heat by the black surfaces of the cans placed on the surface of the wall facing the greenhouse. The heat energy collected on the surface passes to the water with high heat transmission coefficient and is stored. This stored energy is used for heating the greenhouse at night. In addition to water used for heat storage, other liquids and solids are used, such as sodium sulfate and pebble. However, water is a more widely used material both in terms of its long heat storage time and inexpensive cost.

Solar collectors are used to actively use solar energy in heating. Solar collectors are devices of various types and shapes that collect solar energy and transfer heat to a fluid. They are often used for domestic hot water heating. This system consists mainly of 4 main units:

1) Heat collecting unit consisting of solar collectors

2) Heat storage unit where the collected heat is stored

3) Stored heat heated plastic greenhouse

4) Heat transfer unit between heat collection-storage units and greenhouse

During the daytime, the heat energy collected by the solar collectors will be stored in the heat storage unit by the operation of the pump unit in the heat storage unit. Depending on the indoor temperature of the plastic greenhouse, the pump unit inside the plastic greenhouse unit will be operated to recover heat from the heat storage unit. In this case, fluid circulation between the heat storage unit and the heating pipes in the plastic greenhouse unit will be ensured. During the heat recovery periods, the operation of the electric motor moving to the pump unit used for fluid circulation between the plastic greenhouse and the heat storage units shall be controlled by the time clock. When the temperature of the heated water in the solar active heating system is higher than the water temperature (distribution temperature) required to be sent to the greenhouse, the heated water in the system can be used directly to heat the greenhouse. When the temperature of the water heated in the system is lower than the distribution temperature, the water is heated by the auxiliary heating system until it reaches the distribution temperature. This auxiliary heating system may be an electrically operated heater.

In plastic greenhouses, the amount of heat required for heating the greenhouses is found by means of various formulas.

The efficiency of the system was measured and proved to be an extremely economical and environment-friendly system in a project study conducted in an area in Antalya within the scope of solar energy and greenhouse heating system. According to 2016 data, 174 kilograms of fuel, 123 kilograms of diesel fuel, 115 kilograms of LPG and 100 kilograms of fuel were saved on a daily basis.

If solar energy is used in greenhouse heating; The contribution of the greenhouse producer in terms of the national economy, human health and environmental protection is indispensable. Fuel savings are the main advantages. In addition, production costs of products grown in greenhouses will be reduced due to reduced heating costs. Reducing production costs will facilitate the sale of products in the market and will allow consumers to buy greenhouse products cheaply. The foreign energy intake will be reduced and contribution to the national economy will be provided as a great saving will be achieved in terms of the fuel we depend on abroad. Since the carbon emission level is zero, it will also contribute to the environment. Furthermore, the design and installation cost of the heat storage method is low.

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