The potential of building-integrated photovoltaic systems in Zimbabwe and their application to thermal environmental control

Munyati, Edmund (1999) The potential of building-integrated photovoltaic systems in Zimbabwe and their application to thermal environmental control. Doctoral thesis, University of Northumbria at Newcastle.

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Abstract

A strategy has been devised to assist the photovoltaic technology to evolve to the point where it should be a major player in the provision of sustainable energy supplies to loads that are in grid-connected locations in Zimbabwe. The strategy has been devised through an investigation carried out on grid-connected commercial-building loads. The objective of the research undertaken in this programme is to formulate a novel strategy of utilising the photovoltaic technology such that viable financial mechanisms which will provide the funding for the photovoltaic technology in the target area are stimulated.
Many financial mechanisms have been given global impetus but it has been generally acknowledged that the success of all renewable energy technologies is dependent on introducing them in such a manner that local finances are capable of funding them. This can only be achieved by persuading existing financial structures to accept these technologies by penetrating the market which these structures are used to dealing with. The financial structures can then be steered, from within, towards the target market. The strategy also builds on the successes achieved by international donor-funded projects in identifying the market potential of utilising photovoltaics as in the GEF PV projects, and the technical viability of the local industry to support the technology as in the GTZ PV projects. It establishes a new method of increasing the capacity of the photovoltaic systems in the region under consideration to a level where it would set a trend that can accelerate the decrease in the cost of the photovoltaic technology in the local area. This adds a fifth dimension to the four major directions being taken to reduce costs of photovoltaic systems, which are reducing the amount of solar materials used; reducing the amount of energy and
labour used in processing; using alternative manufacturing equipment; and investigating novel solar materials.
The strategy proposed is based on the concept that optimising the perfomance of the energy generating system, optimising the efficiency of the system whose energy load is met by the power system and continually identifying market-efficient applications of the technology on which the power system is based is part and parcel of achieving a sustainable base for the long term utilisation of the technology. It shows the best way of removing the negative view that is widely held that excluding applying the state-of-the-art of a technology in the major markets of photovoltaics, the developing countries, is the only viable
way of achieving development. It also lays the basis for the efficient introduction of smart energy-efficient appliances and novel solar devices such as transparent solar cells and AC modules as well as concentrator technology in future, when these concepts have progressed out of the laboratory.
In this project commercial buildings in a chosen benchmark city were used as the energy demanding load. Photovoltaic arrays integrated in to the building facades were taken as the energy-generating systems. The energy requirements of the air-conditioning plant in the buildings were taken as the parameter for which various control paradigms were investigated in order to achieve the optimum method of utilising energy generated by photovoltaic systems installed on the buildings. The resources used in this investigation included hourly weather data obtained from the benchmark city and building data from the city scape.
Generic and transient building energy simulation computer software tools, TRNSYS and DOE2 respectively, were used to estimate the energy utilisation of the buildings and to test the various control paradigms formulated. A solar resource estimation software program was developed in-house to estimate the available solar energy incident on the various surfaces of the buildings, and a control system
simulation program, MATLAB Simulink, was used to test the performance of the proposed mounting system for the photovoltaic modules.
The project focused on utilising the building integrated suntracking photovoltaic arrays as shading systems. It used a recursive parameter estimation method to predict the reference for controlling the position of the photovoltaic arrays and enable them to fulfil the dual purpose of generating electricity for the building and reducing the air-conditioning load by reducing the solar gains into the buildings through providing the shade for the windows. It also investigated the effect of utilising energy conservation measures such as designing buildings for natural ventilation and thermal massing. Finally an estimation of the reduction of the cost of air-conditioning system on one of the buildings due to shading was made so
that the effect of this reduction on the cost of funding the installation of building-integrated PV can be investigated.
It was generally concluded from this work that: i) utilising building integrated photovoltaic systems in the
target market could lead to a significant contribution to its energy supply; ii) there were convincing reasons why using building integrated photovoltaic systems was a reasonable way to proceed in promoting the technology in the target area because the building market was the only market in the country which had the capital to adopt the systems in a commercial mode, and thus stimulate the interest of the local financial structures; iii) there is need to optimise the load in these buildings before photovoltaics can be effectively incorporated as the major source of energy iv) the acceptability of photovoltaics as the major source of energy differed among building types, but it was generally accepted that the more energy efficient buildings were the ones where photovoltaics could be the main if not the only source of energy; v) an integrated approach to future energy policies was the only way for a sustainable energy supply in the target market; vi) the strategy is applicable on a regional scale because
of the geo-economical location of the benchmark city.
This project investigated the technical viability of the building-integrated of photovoltaic systems in Zimbabwe. Further research on the topic requires demonstration systems of the proposed plants, and an in-depth economic analysis can be made from these.

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