UWE Bristol Engineering showcase 2015

Daniel Lovell
UFMFX8-30-3: BENG MECHANICAL ENGINEERING
Project Supervisor
Rachel Szadziewska
PASSIVE SOLAR GREENHOUSE DESIGN
Controlled environment agriculture (CEA) is an
advanced agricultural technology whereby crops
are grown in controlled environments in order that
horticultural practices can be optimized. Advanced
forms of CEA incorporate hydroponics which
allows more growing variables to be manipulated
compared to soil based horticulture. The most
common controlled environments are
greenhouses; these structures have existed for
centuries allowing people to extend growing
seasons and cultivate crops year round. Early
greenhouses had very few control features and
would have cultivated crops using traditional soil
based methods. However modern greenhouses
have become more automated with the use of
computer technology and are increasingly
incorporating hydroponics in an effort to increase
production.
The energy demands of any controlled
environment will play a major role in determining
the viability of CEA. The key driver for making
them more efficient is the rising cost of energy in
all forms (Figure 4) and the forecast for their
continuing increase. Not only are there concerns
over the rising prices, the security of these sources
in the long run are potentially an issue. This was
the main driver behind developing a passive
design.
A direct gain concept was adopted for the purpose
of this design project. This design concept utilizes
south facing windows in which solar radiation is
directly admitted in to the space. The space
requiring heat input is directly behind the south
facing glazing and there is thermal mass in the in
the walls floors or ceiling meaning the room acts
as both the solar collector and the thermal
storage.
In order to determine the effect of glazing size and
orientation it is crucial to calculate the solar
radiation available to the site, the availability of
solar radiation forms the basis of any passive
design. The chart below shows a small part of the
solar analysis carried out during the project.
More detail solar data was gathered for the
project through the use of special computer
programs, as indicated in the image below.
As a result of all of the calculations and research
carried out an optimized design was proposed.
With a view to taking this further for complete
thermal simulation.
Project summary
The economic viability of greenhouses in the
UK relies heavily on its thermal efficiency. This
report investigates the reason why indoor
cultivation of crops is of interest to UK
farmers and of particular personal interest.
The report outlines research into the current
ways in which the industry is tackling the
efficiency of controlled environments, and
highlights attempts at passive solar design
that have already been made. It also sets out
to propose an optimized design for a specific
location in the UK.
Project Objectives
Investigating mathematically the effect of the
overall shape, size, and orientation on heating
and cooling requirements.
Recommendations for embedded design
concepts based on research undertaken
The preparation of a 3D CAD model of the
proposed passive design, for the intention of
performing CFD analysis.
Project Conclusion
The project was a success as it highlighted a
current passive design and was able to
identify its shortcomings and provide
solutions to combat them. A number of key
design decisions were highlighted as a result
of the research and calculations performed .