Use of Hot Water Obtained From Solar Collectors in the Disinfection of Hotbeds

Abstract

The worldwide restrictions imposed on agrochemicals (pesticides) used in the disinfection of hotbeds have led researchers and employees to benefit from the sun, which is one of the renewable energy sources in agriculture, for this issue. In this study, the usage possibility of solar collectors and solar energy in the disinfection of hotbeds was investigated in Tekirdag Province in Thrace region of Turkey. Hot water obtained from solar collector with an area of 3 m(2) was transported to the hotbeds by using pipes which were laid into the greenhouse and connected in series. Hot water pipes were placed into the soil with the intervals of 50-55 cm. The effect of the hot water in the system on the temperature of soil surface was measured by infrared thermometer and significant differences were observed. The soil surface temperature measured in the greenhouse was measured as 62 degrees C in the parcel where plastic covered and hot water passed. This value was determined as 15.1 degrees C more then what it was in the soil parcel and 10.4 degrees C more then what it was in the plastic covered parcel. The temperature of the hotbed at 10-15 cm depth was measured by digital soil thermometers having probe. Significant differences between the parcels were identified as a result of measurements of soil temperature conducted in plastic covered parcel in which hot water passed and in plastic covered soil parcel. In the plastic covered parcel with hot water, the soil temperature was measured as 50.2 degrees C. The soil temperature in hot water parcel was determined as 15 degrees C more than the soil temperature in soil parcel and as 6.5 degrees C more than what it was in plastic covered parcel. The temperature of the soil at 20-25 cm depth was measured by the soil temperature sensors. In the hot water parcels, the maximum temperature of the soil at this depth was 27.03 degrees C and it was measured to be 2.13 degrees C more than the temperature in plastic covered parcels. In the parcel heated by water coming from the solar collector and the water temperature increased up to 78-79 degrees C in summer, the soil temperature could not be raised to the desired extent. This is because the thermal conductivity of soil is very low. Placing of hot water pipes with more frequent intervals (such as 20-25 cm) can increase the soil temperature more. This may also provide opportunity to achieve the soil disinfection in a shorter period.