Chapter 10. Electronic load-controlled mini-hydroelectric projects: Experiences from Colombia, Sri Lanka and Thailand*

*Prepared by Gary Whitby, Intermediate Technology Industrial Services (ITIS). United Kingdom, on behalf of the ILO.

UNTIL NOW, THE technical constraints to widespread adoption of small hydro plants have been the conventional hydraulic or mechanical governors which control the flow of water through the turbine. This control is necessary to maintain a constant alternator speed which will vary depending on the electrical demand (or the electrical load). However, an electronic device has been developed to control the load on the alternator. This eliminates the need for a flow-controller, reduces the capital costs of the hydro scheme significantly and raises the load factor, thus enabling better utilisation of the available power. The electronic load-controller is a newly emerging technology which expands the scope of application of micro-hydroelectric power and is therefore of particular benefit to rural communities in developing countries. It is now in production in the United Kingdom and is being assembled under licence in Thailand. This chapter examines the application and benefits of the electronic load-controller on micro-hydro installations and the scope for its local manufacture.

In most developing countries electricity for lighting or cooking is rarely available outside the main urban centres, but most of the population lives in rural areas, and therefore cannot benefit from this form of energy. Furthermore, the spread of employment-creating industries to rural areas has been hampered, to some extent, by the lack of power. Planners have tended to concentrate on large, centralised generation, either hydro, thermal or nuclear, and as such have accepted the Western criteria for investment in electrical generating systems. But the diseconomies of electricity distribution with these systems have prevented the resulting power from reaching the rural populations, particularly in mountainous regions where the topography itself prevents wide distribution. An answer to this would be the development of smaller electricity-generating plants installed near the rural town or village. In many areas, micro-hydro power promises to be the most economic alternative for such decentralised power production.

To be economically viable and competitive with alternatives such as diesel power or grid extensions, the capital cost of micro-hydroelectric plants must be kept down by pragmatic design: using simple turbines and minimum cost civil works. For reliable operation in remote rural areas, the technology must be dependable and simple to operate. In the past, and in the absence of an alternative, normal practice has been to scale down conventional large hydro machinery, including the hydraulic governor. But this has proved to be both an uneconomic and an unmanageable approach. Defective mechanical or hydraulic governors have been the main cause of failure in these small hydroelectric plants. They are too complex to maintain at the village level in developing countries.

Recognising this, a hydro engineer and an electronics engineer, both from the United Kingdom, designed a low-cost electronic device to fit into micro-hydroelectric schemes (10kW to 100kW) in order to control the electrical output from the alternator (that is, controlling the “load” rather than the “flow”). Over the past five years, the Intermediate Technology Development Group (ITDG) has assisted a number of developing countries in the development, testing and demonstration of this device. Many additional advantages of the electronic load-controller were demonstrated during overseas tests in Thailand and other countries. These include simpler turbines, lighter penstock pipes and greater electrical usage. Its true versatility has become increasingly apparent as new schemes have been introduced. It has been widely accepted as a major step forward in making micro hydroelectric plants viable for small rural communities.

I. TECHNOLOGY DESCRIPTION

With any type of electrical generating system, as electricity is taken from the alternator, more power is needed to maintain the alternator speed. Thus when electrical appliances are turned on and off, without more power the alternator will slow down and speed up respectively. In order to maintain a constant frequency and voltage, it is crucial that the alternator speed is kept constant. Conventionally, this is done by a flow-controller in hydroelectric generation..

However, with an electronic load-controller the water flow no longer varies. Instead, the turbine is set to carry its full water flow continuously and, therefore, the alternator is driven so that its full available output is generated. To avoid over-speeding of the alternator when appliances on the main load are switched off, the electronic load-controller automatically switches an auxiliary load into the system to exactly compensate for that load which had been removed. This maintains the total load on the alternator and hence a constant speed. Fluctuations in the water flow will automatically be taken into account by the electronic load-controller’s sensing circuits.

The auxiliary load, sometimes known as a ballast load, takes the form of resistance heaters; either space heaters, immersion heaters or storage cookers. These are loads which are not needed at any particular time and which can be switched in and out of the system at will. In some installations, the excess power is merely “dumped”. This may sound wasteful, but flow-control, in effect, dissipates surplus hydraulic power by diverting a portion of the full flow elsewhere; so in energy terms there is no difference. It is unlikely that a small hydro scheme will have a water storage capacity, because of the cost of constructing a dam, so most are “run-of-stream”, that is, the water is diverted from a running stream to the turbine. In this case, there is little likelihood of wasted energy as the water would have run to waste in any case.

The electricity switching is done by modern solid state electronics, controlled by a printed circuit board which senses the change in the load, interprets this into control signals to the electronic switching devices, thyristors, which in turn bring in or switch out the auxiliary loads as required. Two alternator parameters are sensed: frequency of the alternating electricity supply, which is a function of the alternator’s speed; and the current flow in each phase. The electronic load-controller converts both these signals into varying voltage levels, and uses analogue methods to analyse the state of the alternator’s output. Once the controller has determined what is happening to the alternator’s output, the appropriate action is taken by sending control signals to the thyristor firing circuits. There is one firing circuit per phase, and in the case of a three-phase system, the controller can balance the alternator’s output so that each phase is taking the same current flow. This is a dynamic system in which the controller is continually being updated with information, and is continually adjusting the firing angle of the thyristors to respond immediately to the demand on the alternator. This means that the response time of the controller is vastly superior to that of the conventional flow-controllers, and the frequency regulation is superior - a maximum deviation of less than 0.25Hz, with application or removal of full load. This is simply not achievable with flow control.

There are many advantages of this system over the conventional flow control:

(i) Capital costs - the electronic load-controller can be as much as ten times cheaper than the conventional flow-controller - either using hydraulic or mechanical governors - depending on the size considered. This is mainly because electronic components are becoming cheaper as their production technology develops, whereas the technology for producing a flow-controller still requires large numbers of complex machining operations and highly skilled technicians to build and to commission the equipment.

(ii) Maintenance - the number of moving parts in the hydraulic governor and its complexity make it far less reliable than the electronic load-controller.

(iii) Plant simplicity - the turbines can be made simpler as they do not require movable guide-vanes or valves.

(iv) Installation costs - the pipes which take the water from the source to the turbine (known as the penstock pipes) can be lighter as water hammer is eliminated.

(v) Local manufacture - it can be easily assembled in small workshops without the need for special tools.

(vi) Load distribution - for larger three-phase systems, the electronic load-controller will automatically balance the alternator, so that all three phases are loaded equally.

(vii) Application - the system can be easily fitted to any existing hydroelectric plant.

The first electronic load-controller was a very simple single-phase device, and was mainly used on farms in the United Kingdom. In 1979, ITDG became involved with the co-developers of the load-controller to promote the development of a larger three-phase unit for light industrial applications. The initial prototype was tested in Nepal in 1980 during a six-week period. Developing country trials followed commencing with Thailand in 1981. As the designers were involved in these trials, the experience gained from these site visits enabled them to incorporate further improvements. In the early stages of the transfer of the load-controller technology to developing countries, it was found that the conditions of remote villages required a slightly different approach and the technology required minor changes.

ITDG played a catalytic role in establishing a business-oriented link between the United Kingdom designers and the overseas collaborators. To facilitate technology transfer to developing countries, financial assistance was given for the software development - e.g. a training manual, training courses and operational instructions associated with the supply, assembly and installation of electronic load-controllers. This reduced the heavy initial outlay which would otherwise have been borne entirely by the collaborator. Once this had been done the projects were able to continue on a conventional business and commercial basis.

The aim was to develop a useful technology which eventually could be reproduced, utilised and maintained in developing countries. All through the programme this was kept firmly in mind. Even though the electronic load-controller is an advanced technology, ways were sought early in its development to ensure that a significant element of local manufacture using local materials was possible.

The following case studies show the potential of the technology for developing countries and demonstrate not only its technical viability but also its socio-economic advantages.

II. CASE STUDIES

Three cases have been examined to show how the electronic load-controller has merged in with the traditional technologies already in use in three countries chosen. The first explains how the electronic load-controller is the central component of a community-owned sawmill, and the additional domestic benefits which it offers. The second describes how a disused hydroelectric scheme was made operational by replacing the conventional hydraulic governor by an electronic load-controller, and the effect it had on the running costs of the tea factory where it was used. The third describes how local assembly of the controller was made possible with associated cost savings.

1. A Community Hydro Scheme (Colombia)

The Andes in Colombia divide up into three principal north-south mountain chains, which for the most part receive an abundance of rainfall making it one of the richest regions of the world in hydro resources. In 1983, 75 per cent of energy fed into the electrical supply network came from hydro plants, several in the 500 MW to 1,000 MW capacity range. A grid system was constructed in 1971 to interconnect the plants, and now all the main cities and urban centres, where 50 per cent of the population lives, have been incorporated into the system.

Electrical distribution outside the cities is limited to about 15 per cent of the rural population and although efforts are being made to extend it, the high cost of running the transmission lines to areas of very low potential consumption makes this proposal unattractive. Already up to 19 per cent of the generated power fed into the grid is consumed by transmission line losses and, to some extent, by illegal connection.

Traditionally, either animal or water power has been used to work small enterprises such as sugar-cane crushing, cassava grinding, coffee hulling and sawmills; however, many of these systems have fallen into disrepair or have been replaced by diesel engines during the cheap fuel era. In addition to these energy requirements there is now the demand for electric lighting. In the last decade many peasants abandoned the countryside to move to the urban slums where at least some prospects existed for education, health services and “contraband” lighting.

Government plans have been made to meet some of the rural energy demands by building small hydroelectric plants in the 500 kW to 10,000 kW capacity range. However, there is a demand for smaller units which are probably better implemented by the non-governmental sector, but with government support.

In 1982, ITDG funded a water-powered sawmill and electric generator at the small community of el Dormilon in the Department of Antioquia to demonstrate how water power can be competitive with other energy sources in the 10 kW to 100 kW range. This was achieved by designing the plant as a complete energy system to meet both mechanical and electrical power requirements, integrating both productive activity (the sawmill) with the domestic requirements of lighting and cooking.

As the ability of small communities to raise and service loans is limited, it is important to keep the capital costs of the plant down for economic viability. The load-controller was the technical means of achieving this.

Community profile. The community of el Dormilon consists of about twenty subsistence families. Lumbering, extraction of sand and ballast from the river, and coffee growing are the only cash-generating activities. A non-governmental organisation “Comunidad por los Ni#148;, which believes that the strongest motivation of people towards construction activity is in the desire to improve conditions for the benefit of their children, has been helping the community to steadily achieve self-reliant development. The community has worked on a communal project to improve homes, the construction of a school and a concrete bridge over the river. Much of the success of the project relied on the latent creativity and innovativeness of the community which undertook the main construction work and operation of the plant.

The scheme. Had the micro hydroelectric scheme been used for domestic purposes alone, it would not have proved to be economically viable. Therefore, it was essential for the scheme to be coupled with an income-earning activity. In this case sawmilling was chosen; an activity already undertaken in the community by six families, two permanently, and four on an occasional basis. Prior to the project the forestry activity was logging, felling trees from the forest and selling the logs at the roadside to truckers who sold them in the nearby centre of San Luis and Medellin for processing into sawn timber. By having their own sawmill to process the timber, the value added would be increased by up to seven times the unprocessed price.

As mechanical power is required to drive a saw, it was decided to use the shaft power from the turbine directly. But the community was anxious to have electricity in its homes primarily for lighting and, if possible, for cooking. Therefore, it was decided to couple up an alternator to the turbine and control the system by an electronic load-controller. This meant that when power was not being used by the saw for cutting, the electricity generated by the alternator would temporarily increase and the load-controller would divert this into an auxiliary load - heat storage cookers in this case. Over a 24-hour period the storage cookers would have received enough electricity (converted to stored heat) for cooking the family meals. Additionally, the alternator load-controller combination would work together to maintain a constant saw speed; the alternator effectively would act as a brake on the saw, automatically being applied when the saw ran too fast, and released when it was too slow. This would improve the quality of the saw cut, and hence the processed timber which commanded a preferential price in the market.

Each house would receive a cooker as part of the community scheme, and a separate electric supply from the alternator would be given to provide lighting at night when the saw was not in operation.

Financing. The economic justification for the project was determined by a preliminary socio-economic study. The community established itself into a legal entity, the Community Association of el Dormilon (CAeD), with the local “Comunidad por los Ni#148; promoter taking a leading role. CAeD was classified as an agricultural guild association, and as such was able to borrow money. Under a Small Industry Programme financed by the British Overseas Development Administration (ODA), ITDG provided an interest-free loan to CAeD, repayable over five years with one-year grace, to meet the equipment costs. The community provided all the labour to build the power house/sawmill, to lay the penstock pipes and to erect the transmission lines to the houses, the “cost” of this being its contribution to the project.

A work programme was carefully agreed between the members of CAED with allowances being made for old and young villagers. It was agreed that the profits from the sawmill were to be used to repay the loan and provide finance for more community-related projects. Maintenance costs would be covered by the families paying into a central fund the money which they would have spent on kerosene or candles for lighting. This meant that the supply of electricity for cooking was a bonus - very valuable in terms of labour released from wood collection.

This arrangement has proved to be very satisfactory and particularly popular with the women who no longer complain about the unhealthy environment created by smoke from kerosene and wood, or about time spent in lighting fires, collecting wood and washing pots.

Economic considerations. The cost of the project was about US$26,260 (excluding local contribution in the form of labour) which included the cost of the construction materials and mechanical and electrical equipment. The alternator, load-controller and circular saw were imported, but everything else was locally-made or purchased.

The benefits to the community fall into two categories: the profits from the sawmill and the advantages of domestic electricity. The sawmill has a throughput of one metric tonne per day. Logs would sell in the unprocessed form at about US$11 per metric tonne, but when sawn in the form of planks the price would come to US$79 per metric tonne. Taking an average of 250 days per year, the marginal benefits of the sawmill will be 250 × US$68, that is, US$17,000 per annum.

It is difficult to analyse the effect of the load-controller on the economics of the sawmill as it is impossible to say how much extra revenue is generated by the improved cut, but indications from the project are that the planked timber is easy to sell at the prices forecast (mainly because of the quality) and that the revenue projections are in line with the above analysis. Unfortunately, exact details are not available as CAED records are not very comprehensive.

The effect of the load-controller on the electrical supply to the households is more clearly evident. All of the households are paying what they would have spent on kerosene and candles for lighting, which amounts to US$368 per year, but they get free electricity for cooking which saves the community US$805 per year in fuelwood savings (This figure has been calculated on the basis of a market for the fuelwood and the opportunity cost of labour saved in not having to collect fuelwood, and can therefore be considered only as an approximation). Below we consider the annual costs and benefits of the total system to the community.

Costs:
Annual capital charge (6 per cent of US$26,260 over 20 years)	US$2,307
Maintenance (2 per cent of capital)	525
Sawmill labour costs (paid to CAeD members who work alternately)	4,814
	US$7,646
Benefits:
Revenue from sawmill activity	US$17,000
Reduction in kerosene/candles expenditure	368
Savings in fuelwood for cooking	805
	US$18,173

The overall economic advantage is clear. Indeed, from the householders’ point of view, they are paying only US$368 per annum for lighting and cooking. Added to this, their life style will be further improved when the sawmill profits are used for community projects.

Operating experience. The plant has been running for just under a year now (October, 1983) and during this time the storage cookers, incorporated into 15 of the 20 households, have been well received. Every house now has electric lighting.

The teething problems expected in any new industry have been overcome and the sawmill is beginning to achieve the throughputs and profits projected. Based on this, projections for the second year’s production should be realised.

2. Rehabilitation of a Disused Plant (Sri Lanka)

The greater part of Sri Lanka is low-lying and flat, but there is a central range of mountains where peaks rise to 2,500 metres. Rivers radiate from this central massif in all directions. The south-west monsoon brings heavy tropical rain, and in the wet zone the annual rainfall averages about 2.5 metres with up to 7.5 metres in the foothills, making it an ideal place for hydroelectricity generation.

The climate and altitude also enable tea growth and much of the central region is lent to tea plantations run by the two state-owned corporations; the Janatha Estates Development Board (JEDB) and the Sri Lanka State Plantations Corporation (SLSPC). Most of the tea estates have now been nationalised and bought over from the former British proprietors. Because of the ideal conditions for hydroelectric generation, British engineers initiated over 700 small hydroelectric schemes on these estates. However, with the introduction of grid electricity, estate owners were tempted by the lower grid prices and many of the hydro schemes went into disuse.

In 1981, the total installed electricity capacity in Sri Lanka was 501 MW, about 75 per cent of which is hydroelectric power. During the late 1970s, the economy was liberalised leading to a sudden upsurge in the demand for electricity which could not be met. This was aggravated by the lower than average rainfall which constrained the hydroelectric power, and to meet the demand more reliance was put on thermal power. The result was rapid increase in the cost of electricity and subsequently with fuel adjustments of up to 190 per cent depending on the reservoir levels, making electricity cost up to three times the normal amount at certain times of the year.

Worse still was the daily occurrence of power cuts (on average, five hours per day) disrupting industry and having an adverse effect on the tea industry particularly because of the nature of tea-processing.

The high electricity prices and the erratic supply caused concern among the tea estates which looked at their disused or decrepit hydro plants to see how quickly they could be brought into operation. This case study describes how one such unit was rapidly brought into commission.

Hapugastenne tea factory. This factory processes on average 34,000 kilograms of green leaf per day, and is probably one of the largest tea estates in Sri Lanka. It is on the southern slopes of the central massif in the Ratnapura district. Its hydro scheme dates back to 1938 and uses an old Boving peltonwheel turbine which drives a British 82.5 kVA alternator. The control was achieved with a Swedish hydraulic governor which had long since ceased functioning.

During the height of the energy crisis in Sri Lanka, the factory was forced to introduce the hydroelectric scheme to drive fans in the withering process, (which conditions the freshly picked leaf) to save the crop. The lack of control caused by the broken hydraulic governor had resulted in the burning of three electric motors. The hydraulic governor was obsolete, spare parts were unavailable and there was no one who had the technical appreciation of this complex device to repair it. Two solutions were identified by the estate: install a completely new scheme so that a governor could be matched with a new turbine, or find a suitable replacement for a hydraulic governor if the turbine and alternator were found to be serviceable. Close inspection of the turbine revealed that it was in good order, and the alternator could be repaired cheaply. However, a specially designed governor would have to be produced to match the drive mechanism servo output and capacity of the turbine.

ITDG proposed a third, simple operation: to use the existing turbine and alternator with a load-controller. The estate decided to adopt this suggestion and a load-controller was operational within four months of the original site visit as it was a standard item and did not need to be matched to the turbine or the alternator.

The hydro scheme did not have the capacity to supply the total requirement of the factory, averaging at 240 kW, with a peak demand of 420 kW. However, the scheme’s output of 60 kW to 70 kW provided sufficient power to drive the fans in the withering section, which would then be able to run independently in the event of a power cut.

Economic considerations

Costs: A 100 kW electronic load-controller was installed so that it could be used in a larger scheme at a later date. There is little cost difference between this and the smaller units. In 1981, the c.i.f. cost of the device was US$2,750.

The cost of refurbishing the hydro scheme was as follows:

Electronic load controller	US$2,750
Freight and insurance	479
Import duty (12.5 per cent)	404
Alternator repair	1,018
Installation costs	611
	US$5,262

For the purposes of the economic appraisal, the border price of the installation is taken as US$4,857 which is the above figure net of duty. Maintenance cost was estimated at a nominal sum of US$100 per annum, and no additional labour cost was involved as a load-controller did not need an additional operator. The hydro scheme was operated by an existing employee as a marginal addition to his/her existing function. With a conservative estimate of its life as 20 years, the annual costs are:

Annual capital charge (6 per cent over 20 years)	US$424
Maintenance	100
	US$524

This means that the cost from this refurbished hydro scheme is a very low figure of US$ 0.0026 per kilowatt hour.

Benefits: The alternator was wired to the distribution board in the factory so that eight of the 15 fans in the withering section were connected. The average demand was 40 kW, therefore, for 18 hours per day, 300 days per year, and a 90 per cent availability, giving annual savings of about 200,000 kWh, otherwise purchased from the grid.

Although electricity prices are 3.5 us cents per kilowatt hour plus fuel surcharges, the savings to the nation are in respect of savings on the more expensive gas turbines and other thermal stations which are commissioned to meet peak demands. Gas turbine operating costs are 14 us cents per kilowatt hour, and other thermal power costs are 7 us cents per kilowatt hour. Therefore, annual savings to the nation range from US$14,117 to US$29,410.

It is difficult to know how much production has been saved by the introduction of the scheme, but records from previous years indicate that 3 per cent of the crop was lost through grid outages, representing about 100,000 kilograms of tea. The factory production and expansion costs are 67.6 us cents per kilogram, on average. The World Bank estimates that the cost of tea chests and transport of processed tea to the ports is 13 per cent of the total production costs, that is, 8.8 us cents per kilogram.

This is the marginal cost of producing tea. Reductions in tea production losses are valued at an f.o.b. export price, inclusive of government taxes, at US$2 per kilogram less the marginal cost of production (8.8 us cents per kilogram) that is, US$1.91 per kilogram (equivalent to border prices). Therefore, savings of US$1,894 per metric tonne of tea lost are achievable.

Economic Summary

Costs:
Annual costs		US$ 524
Benefits:
	(i) grid savings	US$14,117 to US$29,410
	(ii) lost production	US$ 1,894 per metric tonne saved

Clearly, this represents a financial advantage which cannot be ignored. The payback period is less than six months with the most conservative estimate of benefits.

The most likely alternative to this scheme for the tea estates would be a diesel set, with fuel costs alone amounting to US$1.06 per kilowatt hour, without considering capital recovery, operative wages and maintenance.

3. A Manufacturing Capability (Thailand)

To the west of Thailand is a mountain chain stretching from Burma in the north to West Malaysia in the south, and to the north is a high plateau area from which many streams flow south into the central plain of Thailand. Thailand benefits from the May to October monsoon making the mountain regions suited to hydro schemes.

Despite this, only 16 per cent of national electricity generation is hydro, the remainder being generated from imported oil in either diesel or thermal stations which accounts for an installed capacity of 2052 MW. In 1981, the National Energy Administration of Thailand estimated the potential for mini-hydro plants to be 1066 MW, of which 210 MW could be easily and economically developed under present conditions.

A major government policy is to improve the standard of living of the rural population, a key element being the supply of electricity. As in most developing countries grid extension is not economically viable. Therefore, a small hydro development programme to provide decentralised electricity generation to more isolated communities has been initiated by three main organisations, namely, the National Energy Administration (NEA), the Electricity Generating Authority of Thailand (EGAT) and the Provincial Electricity Authority (PEA).

NEA’s estimate of generation costs below, highlights the advantages of hydro power, and their reasons for pursuing this alternative.

Diesel/generator set	US$0.14/kWh
Oil fired power station	US$0.047/kWh
Hydro power	US$0.018/kWh

To this end, NEA has developed two types of turbine (cross flow and pelton wheels) ranging in size up to a maximum of 100 kW. The generators of up to 500 kW are also locally manufactured. However, the governor had to be imported and in 1981 it cost as much as the combined price of the turbine and generator. Therefore, NEA were anxious to make use of the electronic load controller. Early in 1981, after extensive testing in the United Kingdom, the first three-phase controller was tested at the Kun Krong Forestry Station in Northern Thailand under NEA supervision. This unit has been working since then without any problems.

After the first year of trouble-free operation, NEA entered into negotiations with ITDG to establish a local manufacturing capability to assemble electronic load-controllers in Thailand.

Local manufacture. Soon after the initial testing of the controller in early 1981, an engineer from ITDG visited NEA to start discussions on transfer of technology for local manufacture. At the same time, he investigated the availability and cost of local components so that a kit comprising both local and United Kingdom manufactured components, could be designed and its cost determined.

After a firm expression of interest by NEA in establishing local manufacture, the United Kingdom designer was commissioned to design a manual to contain a description of its mode of operation, fault-finding techniques and assembly instructions for Thailand, and then to undertake a field visit to demonstrate assembly and installation of the unit.

Prior to this visit, a licence agreement was arranged between the United Kingdom designer and NEA to assemble the controller from kits partly supplied from the United Kingdom. The licence was agreed on the following basis:

(i) load-controllers assembled in Thailand were not to be sold outside Thailand without prior written permission;

(ii) confidentiality of the design and assembly instructions were to be observed; and

(iii) controllers were to be assembled strictly in accordance with the instructions, which were applicable to the hardware supplied.

At the time of writing, NEA have assembled six kits with two more on order. They are used for NEA installations at present, and are intended for many of the 75 micro-hydro schemes in their current five-year plan.

This has given NEA a complete domestic manufacturing capability for micro-hydro schemes. At present, the load-controllers are made in the NEA training workshop by the electrical instructors on a part-time basis. It is estimated that two men could assemble three kits per week, although this rate of production is not envisaged for some time.

Cost savings. A completed three-phase 30 kW unit costs ex United Kingdom factory US$2,704; with estimated freight and insurance of US$652, the landed cost in Bangkok would be about US$3,360.

A kit of parts, incorporating the electronic, the SCR (silicon controlled rectifier or thyristor) components, the RFI (radio frequency interference) suppression device, assorted connectors and terminal rails (all not locally available) costs ex United Kingdom factory US$1,039 plus US$198 freight and insurance, giving a landed cost of US$1,237. To complete the controller, NEA has to supply the case, cables, switches, contactors, meters and current transformers, all of which are locally available and cost about US$570, including labour costs to assemble the kit.

The Government of Thailand has laid down the following taxes on imports:

(i) Import duty, 30 per cent, charged on c.i.f. value;

(ii) Business tax, 7 per cent. At the time of import a business tax is levied on the resale price, that is, c.i.f. price, plus import duty plus profit. For the purposes of calculating the resale price at any given time, standard profit rates are laid down in the customs tariff: in this case, 11 per cent;

(iii) Municipal tax is 10 per cent of the business tax.

Therefore, for a 30 kW load-controller, the following multipliers occur:

	Complete unit	Kit
	US$	US$
c.i.f. Bangkok value	3,360	1,237
Import duty 30 per cent	1,008	371
	4,368	1,608
Standard profit 11 per cent	480	177
Resale value for tax calculation	4,848	1,785
Business tax 7 per cent of above	339	125
Municipal tax 10 per cent of business tax	34	13
	4,741	1,746
Local costs to make up the complete kit	-	570
	4,741	2,316

Local assembly thus represents a saving of 51 per cent on the complete unit supplied from the United Kingdom. The savings are made on freight charges (US$210) (less weight with the kits), entry taxes (US$876) and on the cheaper local component and labour costs (US$1,222). This compares also very favourably with the Chinese hydraulic governors imported at a cost of US$5,600 in 1981.

III. CONCLUSIONS

The electronic load-controller is an integral part of the complete system which includes the civil works, electrical and mechanical equipment of a hydroelectric scheme. Therefore, it needs to be evaluated in the context of its effect on the capital and running costs of complete hydro schemes, and on the benefits it has over conventional schemes, namely,

The capital costs of the total plant are reduced as penstock pipe, turbines and the controller itself are cheaper.

The running costs are lower because the electronic load-controller is more reliable; therefore it requires less maintenance.

The controller helps to plan a better distribution of the power available, which tends to help raise the load factor and reduces the kilowatt-hour costs.

The case studies have shown how the controller was demonstrated to be commercially viable to the manufacturer, to the hydro installation organisations, and to the users of the generated power. Therefore, all the key parties have a vested interest in mutually sustaining their relationships, and in continuing to make, install and use the electronic load-controller.

An independent indication of its usefulness has been the reaction from China. During the first three weeks of September 1982, at the invitation of the Chinese Government, a six-man team from ITDG, Evans Engineering and GP Electronics were guests of the Ministry of Machine Building and Ministry of Water Resources at the Hangzhou Regional Research and Training Centre for Small Hydro Power. Since there are over 100,000 small-scale hydroelectric plants operating in China, their interest was understandable. Apart from its economic attractions, the Chinese interest in the electronic load-controller focused on the quicker response times and better frequency regulation it provides.

Extensive tests were held at Hulu-Dong Hydro Power Station, about 100 kilometres from Hangzhou, where the advantages of the device were demonstrated to a number of Chinese hydro engineers. The controller was loaned, for six months, to the Hangzhou Regional Centre which installed it at Lubu Hydro Power Station, Yuyau County, and ran tests for about 300 hours.

After these tests the Regional Centre released an evaluation entitled “Report on the Testing and Trial Operation of an Electronic Load-Controller”. Since the Chinese are recognised as the world’s authority on small-scale hydro technology, it is significant that they should wish to incorporate the United Kingdom-designed electronic load-controllers on hydro schemes in China, in preference to their own flow controllers. ITDG has suggested that arrangements could be made to manufacture the controllers in China, if required.

This chapter has attempted to show how the well-established technology of small-scale hydroelectric power plants has been improved by modern electronic technology. This successful development work has been done not by large engineering companies, but by small private companies who were able to identify the potential for applying the technology in remote rural areas of developing countries. In some cases, ITDG’s role was as a catalyst, but in others, some financial input was necessary in the early stages. Now it is hoped that the technology has been demonstrated sufficiently so that its application and dissemination will spread with the growing awareness that small decentralised power sources are an important means of stimulating the rapid economic development of rural communities.

The field experience of the electronic load-controller in micro-electronic plants has been limited to units of up to 100 kW. ITDG, with the United Kingdom designers, is now looking at newer developments in micro-electronics and solid state switching devices to enhance the controller and to increase its capacity to cover hydro plants presently outside this operating limit.