Adi Quala is an Eritrean agricultural town of 14000 ... the elders were able to have a guided tour of their ... to Eritrea, the technologists designed a new, energy.
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Adi Quala: application of solar photovoltaic generation in rural medical centres Paul Allen ] ean Wei stead Dulas Engineering Ltd, The Old School, Eglwys Fach, Machynlleth, Powys SY20 8SX, Wales, UK TROPICAL DOCTOR,
1994,24, 17-19
SUMMARY
Adi Quala is an Eritrean agricultural town of 14000 people, and is situated about 70 km south of the capital, Asmara and 30 km from the border with Tigray, Ethiopia. On good days electricity was received from Asmara between 0600 hand 2300 h with nothing available outside these hours. These conditions meant the electricity supply had been a constant problem for the Adi Quala hospital which caters for about 50000 people with 21 staff. It was for this reason that it was chosen for the first solar system, which provides all essential requirements completely independently from the grid connection. This will in turn enable the hospital to increase the range and reliability of services on offer. Three weeks after the arrival of the equipment the elders were able to have a guided tour of their new local facilities. This included 2kW of photovoltaic panels (installed on the roof), batteries and control equipment powering a range of hospital equipment used in the Mother and Child Health Centre, delivery room, wards, dispensary, clinic and laboratory. Their enormous appreciation was very moving and well articulated in an afternoon of music, speeches and feasting. Eritrea's first solar powered hospital was welcomed into capable hands. The pilot project was successfully installed and commissioned in February 1992, and has performed well to date. INTRODUCTION
There was music crackling out of the speakers lodged in two trees. A hundred local elders took their seats in the shade of the hospital and awaited the start of the speeches. It was the 29 February 1992 in newly liberated Eritrea and these women and men of Adi Quala were there to celebrate the commissioning of their first fully solar powered
hospital system. The seeds of this project had been sown 7 years earlier when two 'alternative technologists' from Dulas Engineering, UK, had visited Sahel in northern Eritrea. Solar energy was bountiful and an obvious source of power. Medical refrigeration, especially for blood storage and vaccines, was urgently needed, but there was little on the market that was suitable in the circumstances. The performance of bottled gas or kerosene refrigerators is often inadequate and diesel powered systems often suffer from fuel supply problems. Over the year following their first visit to Eritrea, the technologists designed a new, energy efficient, solar powered blood bank, with the Eritreans' problems specifically in mind. The World Health Organization's (WHO) Expanded Programme on Immunization incorporates a major logistical undertaking known as 'The cold chain'. This ensures all vaccines are kept within a limited temperature range throughout their transport and storage. Solar medical refrigeration has played an important part in this venture, particularly in areas where electricity supplies are non-existent or erratic. Extensive immunization programmes are now in progress throughout the developing world in the fight against disease. Over the past 5 years over 2000 solar medical refrigeration systems have been installed. Major programmes are now underway in Zaire, Gambia, Mali, Uganda, Chad, Ghana, Kenya, Mozambique, Sudan and Pakistan. Solar power has much to offer in the field of healthcare. THIS EQUIPMENT
The history of the photovoltaic effect began as long ago as 1839 when the French scientist Bequerel noticed that when light was directed onto one side of a simple battery cell, the generated current could be increased. By the late 1950s NASA had installed a 108 cell photovoltaic array on America's first satellite Vanguard One, and photovoltaics had become an established technology. When light is directed onto the surface of a photovoltaic (pv) cell its electrons become energized in direct proportion to the intensity. When their energy exceeds a certain point a voltage is set up across the cell. This voltage can then be used to drive an electrical current around a circuit and do useful work. Thin discs of very pure silicon, with small amounts of very specific impurities are called photovoltaic cells. Each disc is about 100 mm in diameter, and when exposed to bright sunlight will produce about 1.5 W of low Voltage direct current electricity. These discs are of little use on their own,
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Figure 1. General block diagram for solar medical equipment
so they are combined into PV modules (sometimes called PV panels), that contain around 36 cells. If more power is required than one module can produce they are often mounted side by side and wired together to form a PV array. By altering the way that the panels are interconnected the overall level of power generated cannot be altered but differing voltages and currents can be achieved. Most PV arrays are arranged to charge 12V or 24V batteries. Electrical energy from the PV array is fed to the storage batteries via a controller or 'charge regulator' which prevents damage to the battery by overcharging, i.e. having more energy fed into it than it is designed to hold. Such a charge regulator will often contain a 'blocking diode' which acts like a one-way valve, allowing power to flow from the PV panels to the battery during the day but preventing power loss through the panels during the night. A system will also contain a 'low voltage disconnect' to automatically switch off the loads when the battery has reached around 20070 state of charge, to prevent premature battery failure.
THE PROJECT
Discussions in 1990 between the Eritrean Public Health Programme (EPHP) the Dulas Engineering had resulted in a pilot proposal for the totally solar powered hospital system, specifically designed to meet the medical requirements of the EPHP. The aim of the project was partly to address the immediate problem of providing an electricity supply to the hospital, enabling the use of basic
Figure 2. Central Power Bank System connection diagram medical equipment, and partly to act as a working demonstration of what is now possible with renewable energy. Although the system provides an alternating current supply intended for an incubator or quarterizing equipment, the bulk of the facilities such as vaccine storage, blood banking and ice making refrigerators, operating theatre lights, centrifuge, fans and room lighting have been purpose built or adapted to operate directly from the batteries charged by the photovoltaic power source. The success of this pilot project has led on to a larger second phase project consisting of three similar solar hospital systems each to be installed by a team of local technicians and Dulas engineers in Eritrean rural medical centres by July 1993. These hospitals will incorporate a new design of solar medical refrigerator. This design builds on previous field experience of vaccine refrigeration systems and has been designed to provide the high efficiency performance demanded from solar refrigeration equipment at reduced cost. This is achieved by the
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cabinet having two storage compartments, a 100 I compartment for storing blood or vaccine and a 50 I compartment for ice making. This gives sufficient vaccine storage and ice making capacity to be used at regional or district level within the 'cold chain'. These vaccine and ice chambers are separated by an integral thermal barrier of 100mm thickness and each have their own independent refrigeration circuit for maximum reliability and temperature control. This cabinet therefore avoids the problem of vaccine temperature fluctuation inherent in single compressor refrigerator/freezer designs. RESULTS
A great deal of work has been done on the field testing and evaluation of solar refrigeration systems, most significantly under the WHO Expanded Programme on Immunization and the USAID/ NASA programmes. Over 50 systems in more than 30 countries have been field tested since 1981. From the beginning field trials reported favourable user reaction and correct operation times of at least 83070, exceeding the reliability of kerosene refrigerators. For modern systems correct operation figures of over 95070 are now routine. A World Bank study reported that for existing installations in Gambia 'the experience with solar refrigerators can be considered successful'. It is now generally agreed that the technical barriers to the implementation of solar generation are broken, the only remaining barriers are economic and conceptual. Even these are now rapidly being overcome. Increases in fossil fuel prices, combined with the low maintenance and zero fuel costs associated with photovoltaic systems has greatly improved the economic characteristics for the use of solar power in 'off grid' health centre applications in the developing world. The total PV generating capacity produced world-wide in 1990 amounted to approximately 45 MW, and this has steadily increased since. In the next 5 to 10 years the market still has potential to develop based on a PV module cost of $4 to $6/peak W. Even at this price, PV is definitely the cheapest remote power source for all needs up to a few hundred peak Watts. The next stage of the development of PV technologies is likely to be in the field of automated mass production of cells. We are presently in the middle of an important
development process of 'thin film' PV modules. At the current level of effort, a goal of $1/peak W by the year 2000 is not unrealistic. If the current trend of market growth continues, we may expect an overall world market for photovoltaics by the year 2010 of up to 6000 MW. COSTS
The equipment costs for a basic solar powered portable lamp system begin at around $250. This system will provide around 3-4 h illumination each evening from either a fluorescent 'U tube' for ambient lighting or a searchlight for long distance illumination. Typical equipment costs for a solar powered lighting system are in the region of £1900, typically providing 7·5 h of illumination from each of four strip lights. Equipment costs for a vaccine refrigeration system are typically in the region of £7000. This will give 100litres of vaccine refrigeration plus a 50 litres ice making compartment. The equipment costs for a fully solar powered hospital system, such as the one installed at Adi Quala, are in the region of £37000. The true economic advantages of solar power become evident when the total costs occurring over the predicted lifetime of the project are considered. Although the initial capital costs occurred in solar projects are relatively high, the reliability and low maintenance coupled with zero fuel costs give solar generation systems an overall economic advantage. For off grid electrical loads up to around 10 kW hours/day located in areas with a reasonable solar resource, PV systems provide an exciting economic advantage. The typical daily electrical loads found in most rural health centres and clinics fall well within this figure. Solar power has now become an economic reality for providing power to off grid medical applications in many developing countries, the barriers remaining are: first, in providing the financial environment whereby the initial capital costs can be spread over the lifetime of the project; and secondly, in overcoming the conceptual changes required in accepting this new technology. When these can be successfully overcome there is little to prevent the widespread implementation of solar energy to help meet the growing global demand for decentralized electricity generation.
