**8.1 Heating system**

One of the essential greenhouse installations is the heating system, for the commercial reasons and for creating the suitable indoor climatic conditions. However, it may be the most expensive of the greenhouse installations and a major concern in the vegetable crop production. The system consists of a boiler room with suitable boilers—at least two (**Figure 7**) and an array of pipes which carry, say, the warm water, which is pumped through the pipes, heating the environment. The total area and length of the heat radiating pipes depend on the greenhouse size, water input temperature, both indoor and outdoor air temperatures, and so on. On the other hand, it is the best way to heat the greenhouse indoors as the heat is released evenly, so the air is heated evenly, without major oscillations in temperature. The warm water carrying pipes may be arranged on several levels, particularly along the glass walls. At moderately cold weather, only the first level of pipes is in use. But if the winters are very cold, then the second and third levels may be put in use. In this way, the upper zone is also heated, the zone under the roof, which allows roof glass defrost or snow melt and its discharge.

The heating system has to provide heat that may be lost in various ways:


Nowadays, many types of heating systems are available for the greenhouses. And selecting the proper heating system is important. Some heating systems cost less to buy, or can use less expensive fuels. Others may have a higher initial cost, but they are more efficient, easier, and safer to operate. The most common and least expensive is the unit heater system. In this system, warm air is blown from unit heaters that have self-contained fireboxes. Heaters are evenly located throughout the greenhouse, depending on its volume. These heaters use electricity, which increases its consumption, although the heaters themselves are not expensive. The best and the safest heating system is a central boiler—a boiler room, and a system of *Advantages of Growing Vegetable Crops in Modern Greenhouses DOI: http://dx.doi.org/10.5772/intechopen.101469*

**Figure 7.** *Supplemental lighting lamps (the Netherlands).*

pumps and pipes that distribute hot water or steam. The best system is where the water is heated in the boilers and is then distributed around the greenhouse with a system of pumps and pipes. The warm pipe surface evenly radiates heat and also evenly heats the glass or plastic greenhouse indoors. Types of fuel for the greenhouse heating system may be solid, liquid or gaseous, then electricity (generated

using wind power), and for some time now, the solar power has had an important role in heating various structures, including greenhouses. Types of fuel that are mostly used are fuel oil, coal, wood, biomass (if there is a steady source of biomass), natural and LP gas, geothermal sources. Electricity can also be generated using wind power harnessed by wind turbines erected in windy places and the generator converts the wind power into electricity. And, of course, there is the solar energy, where solar panels convert it to electricity. The cost and availability of these sources will vary somewhat from one area to another or from one country to another. Convenience, investment, and operating costs are all further considerations so as to select a type of heating that is most suitable for modern, successful, and economical crop production. Savings in labor force (or where it is not readily available) could justify a more expensive heating system with automatic controls (**Figures 8**–**12**).

Due to a rapid exhaustion of natural resources that are used for fuel and so in order to be environment friendly, the renewable energy sources are increasingly in use in modern crop growing industry. The renewable energy sources are solar energy, wind and water power, and geothermal springs.

## **8.2 Plumbing and irrigation systems**

The greenhouse plumbing and irrigation system is designed according to the requirements for the particular vegetable crops that are to be grown indoors, a selected irrigation system, and the chemical and biological quality of the water

**Figure 8.** *A boiler in the greenhouse boiler room (the Netherlands).*

**Figure 9.** *A geothermal spring (Serbia).*

*Advantages of Growing Vegetable Crops in Modern Greenhouses DOI: http://dx.doi.org/10.5772/intechopen.101469*

**Figure 10.** *A greenhouse unit heater (the Netherlands).*

**Figure 11.** *Solar panels that convert solar energy to electricity (the Netherlands).*

coming from an available source. Selecting a modern greenhouse irrigation system is an important step as it has to meet all the requirements of the modern vegetable crop production. It also has to be an efficient system as the supply of potable water is in decrease, which goes for the agricultural water, as well. So, the main goal is to achieve high-yield and good-quality vegetables with a highly controlled use of water. The water supply coming from an available source should be of good quality in chemical and microbiological terms. The chemical properties of the irrigation water are very important because the source itself (even the large rainwater collection tanks and ponds near the greenhouse) may contain undesirable elements or compounds, particularly the microelements that even in small quantities can be toxic to the crops or may make compounds that the crops cannot use. Also, the irrigation water may contain compounds (e.g., calcium carbonate) that can plug the plumbing system, particularly if it is a drip irrigation system. There is also a microbiological property of water. The water may contain a number of pathogenic microorganisms that may be harmful to the crops, causing diseases

#### **Figure 12.** *A wind turbine that converts solar energy to electricity (the Netherlands).*

in plants. Moreover, such water may contain microorganisms that are harmful to people, as they may be found in the vegetables we eat (although never in concentrations harmful to people). However, such microorganisms may be found on the surface of vegetables, thus causing some of the infectious diseases in people (due to poor hygiene after harvesting or if consuming unwashed vegetables at our homes). The most common pathogenic bacteria are *Escherichia coli*, *Listeria sp.*, and others.

A recommended irrigation system for greenhouses is the drip system. Due to all the above-mentioned reasons, the greenhouse irrigation system has to be selected wisely, has to be a good-quality one, and well maintained afterward. The quality of water is perhaps the most serious factor when selecting the irrigation system. If the water is of a poor quality, the system will not operate properly and will be hard to maintain. A water analysis may provide the investor/grower with a much clearer picture of the potential problems on a given location, with regard to the water supply and its use in the drip system. Also, a water test may be of help in considering all the possible solutions to the irrigation problems. The water analysis should include tests to pH values, dissolved solid matter, manganese, iron, hydrogen sulfide, carbonates, and bicarbonates. The amount and the size of the particles of certain compounds should be determined, as it determines the size of the emitter filters. The drip irrigation system may provide favorable grounds for the development of bacteria, which results in the formation of sludge deposits and anaerobic environment. Certain bacteria may cause a build-up of manganese, sulfur, and iron

#### *Advantages of Growing Vegetable Crops in Modern Greenhouses DOI: http://dx.doi.org/10.5772/intechopen.101469*

compounds deposits, which may plug the drip system. Furthermore, there are certain algae that may enter the irrigation system from the water supply and build up larger particle deposits. It often occurs when the irrigation water has a high biological activity and high iron and hydrogen sulfide content. The soluble iron compounds (Fe2+) are the primary source of energy for certain bacteria, thus leading to iron deposits (**Figure 13**).

For all the stated reasons, it is important to use the high-quality water, as well as the high-quality system filters, or the poor-quality water may cause a lot of trouble which does not allow the modern vegetable crop production. So, regardless of the quality of water, the greenhouse irrigation water filtration has to be regularly maintained. The system has to be cleaned frequently and the water chemically treated, if necessary. There are some steps to be taken in order to plan further actions: regular basic water quality checkup, water flow and water pressure monitoring, and watching for the color of the water itself. In many countries, the main irrigation water source is rainwater collected in large ponds (wherefrom it cannot leak to the ground) and regularly tested at accredited laboratories where chemical and microbiological content is checked and then, certain measures are undertaken to make it suitable for its safe use in vegetable production (**Figure 14**).

**Figure 13.** *Rainwater pond for the greenhouse irrigation (the Netherlands).*

Drip irrigation system basic components:

