Analysis of Phase Change Materials for Greenhouse Heating Systems

This report explores the application of Phase Change Materials (PCM) in greenhouse heating systems. It begins by outlining the need for alternative heating methods and then discusses various approaches, including water barrels, space heaters, and composting. The report then focuses on PCM, detailing its benefits, such as high thermal conductivity and latent heat values, and disadvantages, like potential supercooling issues. It further explains the working principle of heat pipes, which are crucial for the PCM-based heating system. The methodology section describes the experimental setup, including the materials needed such as a plastic box, wax, thermocouples, air flow meters, a data logger, heat pipes, and evacuated tubes. The aim of the experiment is to reduce the use of gases in greenhouse heating. References to relevant research papers are also included. This report provides a comprehensive overview of PCM's potential in creating more sustainable and efficient greenhouse heating solutions, with the experimental setup designed to evaluate the system's effectiveness.

PHASE CHANGE MATERIALS

GREENHOUSE HEATING
• Other alternatives have to be sought
based on greenhouse needs (Sharif et al.,
2015)
• Different methods are available which
differ in cost, efficiency, materials needed
• Greenhouse
temperatures
should be
maintained steady,
warm and
consistent all
through the
greenhouse
• 25% of heat may be
provided by sun

METHODS OF HEATING
 Water Barrels: Provide an easy way of
saving money in solar heating
 Space Heater: This uses an electric 220 V
space heater
 It is set to a specific time to evade chances
of overheating and increasing bills
 Clean, efficient and safe
 Heater fuelled by gas or oil may also be
used
 Proper ventilation must be ensured when
using wood, gas or oil to heat

Compost
 Compost is placed in a
barrel to heat up as it
undergoes decomposition
(Sharif et al., 2015)
 Carbon dioxide may arise
within the greenhouse
which is beneficial
 Black plastic or
landscaping fabric may be
used around composting
barrels

PHASE CHANGE MATERIALS
 Materials whose phase converts from solid
to liquid and liquid to solid (Sharif et al.,
2015)
 Used in storage of energy for later use
 Benefits
 Able to store large volumes of energy
 Thermal conductivity is greater than one order
magnitude
 High latent heat values
 Ready availability
 Low cost

DISADVANTAGES
 Poor formation of crystal renders
salt very sensitive to super cooling
 Use of paraffin renders it very
flammatory making it not possible
to be used in building environment
 High prices per kilo of plant based
organic matter makes large scale
applications expensive

WORKING PRINCIPLE OF HEAT
PIPE
 Heat pipes are devices of heat
transfer
 Hollow cylindrical pipes filled with
small volumes of fluid which
evaporate to generate heat

Heat Pipe Working Principle

PCM-Heat Pipe solar heating system Incorporation of PCM-HP Solar
Heating Unit into space heating

 Evaporator absorbs heat energy
and makes use of it in changing
working fluid to vapor that then
expands to fill the whole internal
space of heat pipe
 Condenser is in contact with heat
sinks and turns down heat resulting
in the vapor losing heat and hence
condensing to liquid (Kenisarin and
Mahkamov, 2016)
 Liquid returns to evaporator and

METHODOLOGY
Indoor set up

MATERIALS NEEDED
 Plastic box as storage unit
 X kg of wax (melting point at 33-
37⁰C)
 Thermocouples
 Air flow meters
 Data logger
 About 30 heat pipes
 3 evacuated tubes