Compost heat recovery system : pilot-scale study for greenhouse use
Pardo, Emilio (2020)
2020
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2020121027330
https://urn.fi/URN:NBN:fi:amk-2020121027330
Tiivistelmä
The purpose of this project was to build and test a pilot-scale system capable of recovering the heat from compost to be used for greenhouse ambient conditioning. The system was based on Jean Pain’s method and it was carried out at Metsärinteen Puutarha site in Karkku, Sastamala (Finland).
The pilot-scale system consisted of a 12m x 3m x 1.5m (40m3) compost of mixed feedstock (50% woodchips and 50% horse-manure/straw bedding) with 100m of in-compost heat collector coil placed in two concentric layers, separat-ed 40cm from each other. The coil was connected to a set of radiators inside the greenhouse and water was circulated through the system at 5 liters per minute. The test was carried out for 43 days from August to October and numeri-cal data gathered during the test period.
The compost stayed 23 days in the thermophilic phase reaching a peak temperature of 60°C and an estimated average heat energy production of 9600 kJ/h. However, heat collection and release were inefficient, having no impact on the glasshouse conditioning. Ambient temperatures of the glasshouse were mainly influenced by the external environmental conditions.
The calculations indicate the incapacity of the compost used in this study to generate the total heat load required by the greenhouse to achieve optimal growing conditions. The conclusions are based on consideration of minimum average temperatures and solar radiation for an October – April period. Com-post heat production and general system efficiency could be improved by changes in compost design, in-compost heat collector material, and reduced water flow. To achieve better process control, improved in-compost measurements of moisture and temperature are needed
The pilot-scale system consisted of a 12m x 3m x 1.5m (40m3) compost of mixed feedstock (50% woodchips and 50% horse-manure/straw bedding) with 100m of in-compost heat collector coil placed in two concentric layers, separat-ed 40cm from each other. The coil was connected to a set of radiators inside the greenhouse and water was circulated through the system at 5 liters per minute. The test was carried out for 43 days from August to October and numeri-cal data gathered during the test period.
The compost stayed 23 days in the thermophilic phase reaching a peak temperature of 60°C and an estimated average heat energy production of 9600 kJ/h. However, heat collection and release were inefficient, having no impact on the glasshouse conditioning. Ambient temperatures of the glasshouse were mainly influenced by the external environmental conditions.
The calculations indicate the incapacity of the compost used in this study to generate the total heat load required by the greenhouse to achieve optimal growing conditions. The conclusions are based on consideration of minimum average temperatures and solar radiation for an October – April period. Com-post heat production and general system efficiency could be improved by changes in compost design, in-compost heat collector material, and reduced water flow. To achieve better process control, improved in-compost measurements of moisture and temperature are needed