Hydro Power for Remote Medical Clinics
Electricity Supply for Remote Medical Clinics
Using micro-hydro with battery storage by Dave Lambert
There are tens of thousands of medical clinics in the lesser developed countries of the world which do not have access to mains power. This lack of power is a serious obstacle to improving the health of villagers:
- Refrigeration for vaccine storage is only possible using gas or kerosene.
- Lighting for medical procedures, education etc. is only available using poor quality and expensive torches, gas or kerosene lanterns.
- The use of radio, TV, VCR for communication, education and recreation is greatly restricted.
- Cooling fans are not available.
- UV water sterilisation is not possible.
It is difficult to retain good staff at such clinics without power. Medical and nursing staff usually come from the provincial cities. When placed in un-powered clinics they often feel depressed, isolated and restricted in their ability to assist their clients.
Options for power provisions
During the past few decades, several types of generators have been used in such clinics to provide power:
Petrol/diesel The capital cost of fuel generators is relatively cheap, but running and maintenance costs are very high. The supply of fuel to remote areas is often difficult and expensive. Running costs are high because the generator must be sized to handle the peak load when every appliance is in use.
Solar/photovoltaic Solar panels are one of the most reliable products made today. They typically have a warranty of 10-20 years with a design life of 20-40 years. However, they are characterised by a number of problems in difficult field conditions:
- Local personnel do not understand the technology so even 'simple' matters like preventing shading on the panels from trees etc can cause failure.
- Solar installations require a large battery bank. These are heavy, dangerous and need routine maintenance. They require periodic replacement and are easily ruined by the use of impure water etc.
- Large areas of the tropics, particularly in Asia and South America, have high seasonal rainfall and relatively poor insolation (sunshine).
- Solar panels have a very high capital cost.
Hydro power Until recent times, the use of micro-hydro generators (MHG) was limited to units of 2kW and larger. Their output voltage is typically that of the local main grid supply, i.e. 230V AC. These are usually provided for overall village electrification as opposed to an installation dedicated solely for medical clinic use. In general terms, MHG can provide reliable power at an economical cost with few environmental problems. However, such MHG do have some disadvantages:
- They use penstock (supply) pipes of typically 100-600mm in diameter and their design and installation requires highly skilled civil engineering staff. Road access to the site is usually required for delivery of the pipe, concrete, reinforcing steel etc.
- They have an efficiency problem similar to fuel generators in that they must be sized to cope with the peak load. This means that generally 50% or more of the produced power is 'wasted', usually through the use of a load dump such as a bar or immersion heater.
Smaller MHGs (200-500W) designed for battery charging tend to overcome the above two problems associated with the larger 230V-type MHG. They generally weigh less than 25-40 kg and the penstock is usually lightweight poly pipe of 25-75 mm in diameter. Such units can usually be installed in a day by a local electrician and plumber. Smaller MHG systems can be incorporated with solar or wind power sources.
If a large MHG breaks down, repairs must be done on site. However, with the small MHG units, the faulty part can be mailed or delivered to a service centre.
These units have the advantage of using and storing all the available power. However, they do require battery storage and the use of an inverter if 120-230V AC is required. A 200-500W battery charging MHG can often power a system that would require a 2000W MHG operating at continuous main grid voltage (i.e. 230V AC). However, unlike a solar energy system which requires 5-20 days of battery storage (to cope with a week or more of cloudy weather), a MHG requires very little storage in a typical installation because the power is produced continuously, regardless of weather conditions. Arguably a storage capacity of several hours could be sufficient to cope with the peak load, say, from sunset to bedtime when all the lights and TV are on.
Besides reducing the battery size to some 10% of that required in a typical solar system, the quality of battery used on a MHG can be lower. Solar batteries are regularly cycled (discharged) and hence must be of a costly deep-cycle design. Batteries for a MHG should not be subjected to such deep cycling and therefore automotive or truck batteries, which are far cheaper and more readily available, should give 2-3 years of life in a MHG installation.
Until recently these MHG battery chargers used a car alternator as a charger. These are relatively cheap and can usually be serviced by a local automotive mechanic. However, such car alternators have a number of inherent problems:
- They require 10-50W of power to excite the windings, which creates an inherent inefficiency in the system.
- They have brushes that wear out every few months.
- They are not designed for a continuous duty cycle or to be in a dirty or wet environment.
- Their voltage is generally limited to 12 or 24V nominal, which limits the transmission of the power to around 50m. This means that the MHG must be located very close to the water supply, which greatly limits their suitability.
A new MHG battery charger now commercially available (the Rainbow Pelton Hydro Generator) from the Rainbow Power Company Ltd., overcomes the design problems of car alternator type MHG systems. It uses a standard three-phase 0.55kW induction motor which has several features:
- There are no brushes to wear out.
- It uses standard 6204 bearings which are easily replaceable.
- It produces power at 200-300V AC, which means the power can be transmitted several hundred metres or more to the battery charger.
- It is designed for continuous duty and to operate in moist environments.
- It can be connected and serviced by any competent electrician.
The unit produces useful power over a wide range of heads (pressure) from 10 to 100m and with a flow rate between 0.5 litres/second to 7 litres/second.
Typical MHG Installation
Let us assume there is a relatively good site and the MHG produces 15 amps at 12V, or 360 amp hours/day, which is equal to 15-20 60W solar panels, depending on the season and their location (insolation). The MHG in this installation could run 10 fluoro lights, vaccine fridge, TVNCR, radio, ceiling fan and UV water steriliser.
A rough costing for the equipmentMHG completeUS $1475300W sine wave inverterUS $470230 amp hour battery (12V)US $215TotalUS $2160
(The cost of poly-pipe and internal wiring is extra)
A comparable system using solar only20 x 60W solar panelsUS $67001100 amp hour battery (24V)US $2680Regulator and control boardUS $470InverterUS $470TotalUS $10,320
Reliability and ongoing costs
This MHG type has been in production for seven years. Units are in operation across Australia as well as in the Philippines, Papua New Guinea, Indonesia, Vanuatu, Ecuador and Peru.
The only parts subject to wear are the jets (nozzles), runner (wheel/turbine) and ball bearings. Under normal operation, these parts should last several years or more. They are easily replaceable and economical to purchase. These ongoing costs are easily offset against the cost of replacing the large, expensive batteries in a solar-based system.
The entire electronics box weighs only 3kg and could be airmailed or couriered to a service centre in the unlikely event that it required repair.
A MHG can be a very reliable and cost-effective form of remote area power. In the wetter areas of the world it can be more reliable and cost-effective than a solar energy system.
Dave Lambert is Export Manager for Rainbow Power Company Ltd, Nimbin, NSW, Australia.
This article is based on a paper prepared for the WHO Immunisation Programme. It is reprinted from 'The World Directory of Renewable Energy; suppliers and services. 1995'