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close this bookPhotovoltaic Household Electrification Programs - Best Practices (WB)
close this folderTechnical requirements
View the document(introduction...)
View the documentHardware design
View the documentStandards and specifications
View the documentOther technical considerations
View the documentQuality control
View the documentMaintenance services
View the documentEducating users


7.1 Customer satisfaction is the primary goal for a solar home system initiative.
Users play a larger role in PV household electrification than in traditional grid-based rural electrification programs. When satisfied with the service they receive, users are more willing to forgive occasional lapses in the power supply and to make payments promptly.
The project is consequently more likely to meet its financial goals. Providing satisfactory service requires high-quality products and responsive, ongoing maintenance and support services.

7.2 Solar home systems need to be designed to meet customers' expectations at a cost that matches customers' capacity and willingness to pay. A well-designed and constructed system should be reliable, easy to use and maintain, and require minimal care to keep working properly. Users will want to be able to upgrade their systems as their income allows. Systems should be designed to accommodate such expansion. Ultimately, however, users will be happy with their systems only if they fully understand how the units work and accept their limitations.

Hardware design

7.3 All system components should be of the highest quality. This refers to modules, controllers, lights, wiring, switches, batteries, connectors, and module supports. Design budgets should be treated as guidelines, not as a project's highest priority. High-quality systems will out-perform cheaper ones and help ensure the project's sustainability. An appropriate indicator is the lifecycle cost of the project, which takes into account the cost of warranty and maintenance services and the effect of possible non-payment of fees. For example, in remote sites where service costs are high, it may be more cost-effective to provide an over designed system with high-quality batteries instead of a system designed with tighter performance margins. Where affordability is an issue, users can be offered several system sizes and made aware of the trade-offs between system capabilities and costs. Users can then make an informed choice from a range of system sizes, based on their own requirements and their ability to pay. Systems can be designed to allow for future upgrades. For example, one supplier in Indonesia offers a PV module support structure that can accommodate two modules, although the base system has only one. The controller is capable of handling the power output from two modules, and the distribution panel also allows for adding more outlets and lighting circuits.

7.4 Future household PV initiatives can learn from the successes and problems encountered in similar programs to date and improve procurement specifications and technical infrastructure. Specific technical requirements for solar home system components are discussed below.

7.5 Modules. The PV module is generally the most reliable component of the system. In all four country programs reviewed, module failures or even breakages were rare. Preference should be given to modules that meet JRC 503 or equivalent specifications and to suppliers offering at least ten-year performance warranties.' Countries such as Sri Lanka and India, with local module manufacturers that do not meet such specifications, may have import barriers that limit the availability or raise the cost of modules meeting JRC 503 or equivalent performance specifications. In such cases, if removing the trade barrier is not a feasible option, local suppliers must make sure their products meet specifications and offer enforceable ten-year warranties.

7.6 Crystalline cell modules with 36 cells should be used instead of 32-cell "self-regulating" modules. The benefits from improved performance, particularly in hotter climates, more than outweigh the added cost of the charge controller required for the 36-cell module. All modules currently being installed in Indonesia, Sri Lanka, the Philippines, and the Dominican Republic are the 36-cell type. In the initial stages of PV dissemination in Sri Lanka, 32-cell modules were used to avoid the cost of a controller. The suppliers soon realized that the benefits of using 36-cell modules outweighed the added cost of the controller, and installations now use the 36-cell module.

7.7 Module terminals should include lock washers, nylock nuts, or other devices to assure that the terminals do not loosen during the life of the module. Preferably, only modules with a single-junction box should be used. In the Philippines' household PV program, some modules with two junction boxes were supplied. As a result, the cable had to be stripped to separate the two leads, exposing them to the weather and possible corrosion.

7.8 Module Support Structure. The PV module support structure should be corrosion resistant (galvanized or rustproof steel or aluminum) and electrolytically compatible with materials used in the module frame, fasteners, nuts, and bolts. The design of the module should allow for proper orientation, tilt, and, as has been noted, easy expansion of the system's capacity. Roof mounting may be preferable to ground or pole mounting, since it requires less wiring and reduces the possibility of module shading. The module support should be firmly attached to the roof beams and not loosely attached to the roof tiles. The module or array should not be placed on the roof but kept 10-50 cm above the surface itself, to allow cooler and more efficient operating conditions. If the module is mounted on a pole, the pole should be set firmly in the ground and secured with guy wires to increase rigidity. Pole-mounted modules should be accessible for cleaning but high enough above the ground to discourage tampering.

7.9 Charge and Load Controller. The charge and load controller prevents system overload or overcharging. In the past, some programs have not paid adequate attention to the controller. Unsuccessful attempts were made in Sri Lanka to operate solar home systems without a controller or with only a simple charge indicator (a simple controller that provides a low-voltage disconnect (LVD) and charge indication has since been added). Poor-quality controllers have also caused problems. In the Philippines, for example, problems caused by low-quality, locally manufactured controllers were resolved when the controllers were replaced with high-quality, imported components. To operate reliably, the controller design should include:

· A low-voltage disconnect (LVD);

· A high-voltage disconnect (HVD) which should be temperature-compensated if wide variations in temperature are expected in the battery compartment. Temperature compensation is especially important if sealed lead-acid batteries are used;

· System safeguards to protect against reverse polarity connections in the DC circuits (reverse energy flows through the PV module(s) short circuits in the input or output terminals) and lightning-induced surges or over-voltage transients; and

· A case or covering that shuts out insects, moisture, and extremes of temperature.

To enhance the solar home system's maintainability and usability, the controller should:

· Indicate the battery charge level with a simple LED display and/or inexpensive expanded scale analog meter. Three indicators are recommended: green for a fully charged battery, yellow for a dangerously low charge level (pending disconnect), and red for a "dead" or discharged battery;

· Be capable of supporting added modules to increase the system's capacity;

· Be capable of supporting more and bigger terminal strips so that additional circuits and larger wire sizes can be added as needed (this is necessary to ensure that new appliances are properly installed); and

· Have a fail-safe mechanism that shuts the system down in case of an emergency and allows the user to restart the unit.

7.10 Field surveys suggest that most controllers have some (but not all) of these characteristics. However, even highly sophisticated controllers must be tested and proven in the field. A sophisticated new controller that was used in the Pansiyagma project in Sri Lanka created problems which led to user dissatisfaction, poor cost recovery, and serious skepticism regarding PV programs elsewhere in the country.

7.11 Battery. The battery that is most often used in solar home systems is a lead-acid battery of the type used in automobiles, sized to operate for up to three cloudy days. Automotive batteries are often used because they are relatively inexpensive and available locally. Ideally, solar home systems should use deep-cycle lead-acid batteries, which have thicker plates and more electrolyte reserves than automotive batteries and allow for deep discharge without seriously reducing the life of or damaging the battery. In a well-designed solar home system, such batteries can last over five years. However, deep-cycle batteries are not usually made locally in developing countries and high duties often increase the price of importing such batteries.

7.12 In Indonesia, a good-quality automotive battery in a well-designed system can last three years or longer, if the battery is well maintained and rarely subjected to deep discharges; the average daily discharge should be limited to about 20 percent of battery capacity. For example, lightly stressed automotive batteries in the Sukatani, Indonesia PV project had exceptionally long life -- 75% of the batteries last nearly five years (Panggabean, 1993). Field investigations in Sri Lanka reveal that poor-quality materials and questionable workmanship have led to random cell failures in some locally-made automotive batteries and shortened battery life to about two years. Solanka has introduced an extended warranty program that guarantees the performance of the entire system (including the battery and light bulbs) for two years for a fee of Rs 500 ($ 10).

7.13 Battery Mounting. Batteries are sometimes left exposed on the ground and accessible to children. The potential dangers (burns from battery acids, shorts, and explosions) highlight the need for a well-designed battery enclosure to maximize safety and minimize maintenance. Such enclosures are being introduced in Indonesia and the Pacific Islands. Made of injection-molded plastic or fiberglass, the enclosure contains the battery, charge controller, charge indicator, and switches. The electronic elements are isolated from the battery, and the battery enclosure has vents to disperse gases and channels to divert any acid overflows. There is no exposed wiring and the battery can be checked and filled easily.

7.14 Lamps, Ballasts, and Fixtures. The principal reason most householders acquire a solar home system is that it provides brighter, safer, cleaner, and more convenient lighting than kerosene lamps. Users tend to have more "lighting points" after they acquire a system. Field observations show that the additional lights increase satisfaction with and acceptance of the solar home systems. In many cases, householders have subsequently added additional lights to their system while maintaining the overall level of energy consumption (systems with 12 lights have been observed in Indonesia).

7.15 Efficient lights (CFL or tube lights) are usually preferable to incandescent lights. However, fluorescent lamps require well-designed ballasts that ensure an operating life of the tubes of more than two years and that do not interfere with radio or television reception. In some programs, such as Bolivia's, fluorescent light ballasts have been the most problematic component of the system.

7.16 Low-watt (1-2 W) incandescent lights may be preferable in cases where low-level area lighting is needed for short periods (less than 1/2 hour per day) or intermittently (such as in bathrooms or secondary bedrooms). A choice may also need to be made between supplying high-efficiency fluorescent lights (tube lights with preheating elements or CFLs) or locally available low-efficiency tube lights. While the high efficiency lights can offer lower lifetime costs, users may become dissatisfied if they are not available locally.

7.17 Fixtures with reflectors are recommended to increase the effectiveness of the lights. Fixtures that use diffusers must be sealed against insects, since the "useful light" output and efficiency of the fixtures with diffusers can be drastically reduced by a buildup of dirt and insects inside.

7.18 Wiring, Switches, and Outlets. Solar home systems should have high-quality switches and outlets (preferably rated for DC operation). In Sri Lanka, standard AC surface-mounted wall switches were used along with two-prong AC wall outlets. If the lights and appliances draw little current, these AC switches and outlets are satisfactory substitutes for DC-rated components.

7.19 Undersized wiring is sometimes used in solar home systems, particularly when additional light fixtures are installed. This practice leads to energy losses and unacceptable voltage drops and should be strongly discouraged. All wiring should be stranded copper, sized to keep voltage drops to less than 5 percent between battery and the load. Since DC electricity has a polarity that must be maintained, insulation color conventions or labeled wires should be used (red for positive, black for negative, green or bare wire for the grounding conductor). The four country field surveys uncovered several twisted wire or spring-clip wire connections. These do not provide a good electrical connection and should not be used. Soldered or crimped connections or screwed terminal block connectors are the best choices. Soldered wire connections require a non-corrosive rather than an acid-flux solder, especially in regions where corrosion can be a serious problem. As in any electrified home, the wiring should be neatly and securely attached to the walls, either on the surface, in conduits, or buried inside the walls.

7.20 Solar home systems should also have a distribution panel that allows users to connect additional loads simply and safely, utilizing the circuit protection and LVD features of the controller. In Sri Lanka, the panel is a simple terminal strip or similar connection point that allows secure and reliable connection of multiple loads. The terminal strip is located at the regulator, in a separate distribution box, or in the battery box. The distribution panel must always be used if additional circuits are to be installed. Direct battery connections must not be made.

7.21 Other Appliances. Any appliance that operates on electricity can be powered by a solar home system, if the system has sufficient capacity. In the four countries surveyed, the most widely used appliances (other than lights) were black-and-white, 15-inch televisions and radio/cassette players. Users in the Dominican Republic expressed a desire to operate other appliances, such as refrigerators, irons, and VCRs. However, most of the users do not have the capacity to pay for larger systems and the availability of DC-compatible appliances such as color televisions and fans is limited. These users will have to save to buy larger systems. Appliances with high energy requirements, such as irons and air conditioners, cannot be used with small systems, since converting DC to AC electricity involves additional costs and energy losses. Large 1-kWp systems supply 100 kWh/month to customers of Southern California Edison. This is the equivalent of supply grid-quality AC power and is sufficient to operate most of the appliances found in a typical American home.

7.22 Inverters. Customers requiring AC electricity will need an inverter to convert the DC electricity from PV systems. It is very unusual for users with systems smaller than 100 Wp to require inverters (none was observed during ASTAE's field investigations). In any case, the cost of an inverter and associated energy losses recommend against its use in small systems. Several types of inverters are available: square wave (the least expensive and least efficient), modified square wave, and pure sine wave (the most expensive and most efficient). If needed, the inverter with lowest life-cycle cost should be selected. Small inverters dedicated to the specific loads that require AC power should be used rather than a centralized inverter for all loads.

Standards and specifications

7.23 Government or independent agencies should either set performance standards for solar home systems or, in programs utilizing government funds, should require that the system components meet internationally recognized performance standards for modules, controllers, other electronics, and batteries. These standards need to be effectively enforced, as has been done in the Indonesia BANPRES Project. BPPT, as the executing agency, established system specifications for procuring the solar home systems, based on information obtained from consumer surveys and field tests of several solar home system types. The BPPT Solar Test Center was also used to evaluate various system configurations. Each country need not establish its own standard, but can adopt those established by the international PV community.

7.24 Both prescriptive and performance specifications have been used for procuring solar home systems. Prescriptive specifications outline the requirements for each major component. For example, they may specify the size of the PV modules, the battery capacity, the wattage or lumen output of the lamp, the wire sizes, and the controller set points and safety features. This approach has been used in the GEF-financed Zimbabwe PV Project and the Indonesia BANPRES Project and is included in the proposed World Bank/GEF assisted Indonesia Solar Home Systems Project. Prescriptive specifications are easier to implement and make verifying compliance with the requirements relatively simple. Performance specifications detail the output or service which the solar home system is expected to provide. They may specify the number and lumen output of the lights, the average hours of lighting needed at each light point, the watt-hours of other appliances, and the loss of load probability or availability. The supplier then determines the system configuration according to site conditions and performance requirements. This approach is used in the World Bank/GEF-assisted India Renewable Resources Development Project. Performance specifications give suppliers greater freedom to optimize the design configuration but can make verifying system performance difficult.

7.25 Enforcing solar home system standards should be easier under ESCO or leasing arrangements that involve bulk or high-volume purchases. Ensuring performance standards is more difficult in a less-structured program that may not provide customers with the information necessary to judge the quality of the system. A PV systems mechanism rating similar to the UL rating system in the United States and the KEMAKEUR system in Europe would be a useful guide for consumers.

Other technical considerations

7.26 Spare Parts. Fuses, light bulbs and other spare parts that need to be replaced frequently should be available locally from a dealer accessible to users. The minimum quantity of spares that should be stocked depends on the number of systems in the area and the location of distributors. Table 7-1 lists the recommended minimum number of spare parts for a local cooperative in Indonesia that serves 20~2,000 consumers.

Table 7-1. Suggested Spare Parts List for a Cooperative in Indonesia


Recommended Quantity of Locally Stocked Spares

Photovoltaic Module

1 per 250 systems

Charge Regulator

10 per 250 systems


250 per 250 systems spread out over the 2nd and 3d year after installation

Wire, Connectors, Tape

50m wire and 50 connectors (varies with village ability to purchase additional appliances)

Lamp Ballast

25 per 250 systems

7.27 Battery Recycling. High priority should be given to battery recycling in order to minimize environmental contamination and safeguard users. Recycling is most effective in organized programs led by an ESCO or an intermediary. Current battery-recycling programs in the four country solar home system programs reviewed show mixed results. As part of the Solar Energy Program in the Philippines, NEA-GTZ introduced a successful battery-recycling scheme that allowed users to exchange old batteries (for which the manufacturer paid $4.00) through the rural electric cooperative. In West Java, Indonesia, old batteries are collected from each house and recycled by independent operators, who pay householders $2.50 per battery. (However, battery recycling is rare in other parts of Indonesia, where batteries are used less widely and transporting them is difficult.) In Sri Lanka, batteries can be taken to a dealer or a recharging center for recycling, but many users consider the recycling payment, which was about $1.00, too low to warrant returning the old batteries. To increase the volume of battery recycling, the payment was recently doubled. While there is no comprehensive battery-recycling program in the Dominican Republic, it is estimated that about 50 percent of the batteries are recycled.

7.28 Warranties. The four country case studies show that ten-year performance warranties for modules are commonly available from many suppliers and should be required in a solar home system program. Warranties for controllers and other electronic components may range from three months to three years and those for batteries from one year (for automotive batteries) to three years (for deep-cycle batteries). Overall system warranties are also offered for up to one year. However, realistic provisions for enforcing warranties must be in place in order to protect consumers.

Quality control

7.29 The solar home system programs in Indonesia, Sri Lanka, the Philippines, and the Dominican Republic demonstrate the importance of quality in manufacturing of systems and their installation. The need for quality assurance extends to component purchase as well as system assembly, testing, and installation. Solar home system installation should always be entrusted to trained technicians.

7.30 Quality assurance directly impacts the profitability of the solar home system business. Experience in China and Sri Lanka clearly shows the link between significant cost savings and high-volume procurement from reputable manufacturers of quality electronic components used in manufacturing controllers, switches and lights. Due to their low volume of production, system assemblers in China and Sri Lanka currently purchase components from local retail stores, where quality is suspect. This necessitates testing every key component (transistor, capacitor, inductor, etc.) for quality before assembly, thus reducing manufacturing productivity. Lower volume procurement from sources where quality is not assured also results in a higher percentage of returns, increased cost of warranty services and general decline in consumer satisfaction.

7.31 Some suppliers provide packaged kits that include all the solar home system components, lengths of wiring, bolts' nuts, terminal strips, wire connectors, and other hardware needed for each system. This prepackaged kit ensures that the installer uses only recommended equipment and will not have to improvise in the field. The installer also needs proper tools, including multimeter, compass, spirit level, hydrometer, and templates for tilt adjustment.

7.32 How well a solar home system is installed is as important as the quality of its components and assembly. Suppliers should develop installation standards and acceptance test procedures and require that these be used. Any "checklist" should include instructions on how to:

· Install the module (orienting it correctly, avoiding shading, minimizing wire runs, ensuring that the module support is securely attached to the roof beams, tightening the connections, and sealing the junction boxes);

· Locate and fasten the controller and battery enclosure properly;

· Attach switches, outlets, fixtures, and wiring (including which wire sizes to use, how to attach components neatly and securely to walls and ceilings, and how to secure electrical connections);

· Boost the battery charge before installation;

· Check all connections and ensure that the system operates properly before it is handed over to the user;

· Teach the user to operate the system safely; and

· Provide the user with the appropriate documentation, including warranty information, and any spare parts, if supplied, such as fuses and distilled water.

Maintenance services

7.33 While the simple design and dependability of most solar home systems allows a single technician to service a large number of customers, the need for local technical support remains. Users can perform simple maintenance functions. However, field experience shows that very few households can service their system themselves over a long period of time. Solar home system programs are typically used in sparsely populated areas, serviced most effectively by local representatives (preferably from the same village) who can tend to problems in a matter of hours or days, rather than the weeks that might be required with service provided from a central location. The number of technicians required in a service territory depends on the number of systems in use, their quality, and their accessibility (remoteness, road conditions, and available transportation). A rule of thumb in the Dominican Republic is that no system should be more than 50 km from a service center. In Indonesia, both the government-sponsored BANPRES Project and some private dealers use local cooperatives to administer programs, collect fees, and provide maintenance services. The Tuvalu Solar Electric Cooperative Society in the Pacific Islands has local user committees that arbitrate disputes between users and technicians concerning fee collections, disconnections, and poorly functioning systems and keep users informed about the organization's activities. These local networks offer effective support for technicians and help ensure the longterm sustainability of the programs themselves.

7.34 Technicians should be trained in the installation, maintenance, troubleshooting, and repair of systems. Administrative staff must be conversant in program management, accounting, collecting payments, and procedures for disconnecting or removing systems. Well-trained staff are essential for a sustainable solar PV program. Whenever possible, technicians should be used from the villages where the systems are installed. While the simple design and high reliability of solar home systems enables a single technician to cover a large number of customers, it does not eliminate the need for local technical support.

7.35 Solar home system technicians should pass basic certification examinations and also attend periodic refresher courses. Adequate salaries and benefits are required to keep trained technicians on the job in rural areas, and there must be enough business in a service area to support the fixed overhead costs of providing technical services. In Indonesia, service fees from at least 500 systems are needed to pay one technician's monthly salary. (The local cooperative charges a service fee of Rp. 500 per month per system, and the technicians receive a monthly salary of about Rp. 250,000.) The technician may be able to earn extra money by providing other services, such as adding light fixtures to existing systems or new installation. Households should be encouraged to use trained technicians for such procedures. User and technician training should stress the importance of using only approved wiring and connectors.

7.36 Documentation. A solar home system program should have documentation, including:

· A technician's manual that describes the system and includes a guide to procedures, maintenance, and troubleshooting. The manual should also contain graphics such as functional block diagrams and schematics;

· A recommended lists of tools and spare parts to be stocked at the local level;

· Procedures for receiving and responding to user requests in a timely manner;

· Standardized technicians' logbooks for recording system maintenance and repairs;

· Warranty and loan agreements;

· Tariff structures and payment terms and conditions;

· Organization and management plans; and

· User manuals and consumer education literature in an easy-to-understand booklet in the local language, or in "comic book" style.

Educating users

7.37 Customer satisfaction with solar home systems also depends on the user education provided by program administrators, technicians, and suppliers. The education program should cover routine maintenance procedures such as watering batteries (including how to collect clean rainwater if distilled water is not readily available), interpreting control panel information, managing loads, solar access, and replacing fuses and bulbs. Customer education should also make clear the capabilities and limitations of the particular solar home system.

7.38 "Overselling" the capabilities of solar home systems can quickly lead to customer dissatisfaction and poor repayment levels. In the Pansiyagama Project in Sri Lanka, overzealous promoters showed videos of PV-operated sewing machines, pumps, and power tools to prospective customers. The 21-Wp and 52-Wp systems subsequently installed under the project could not run these appliances. This resulted in unhappy customers and service problems in collecting fees. Educating users about recurring system costs, particularly the need to replace automotive batteries every two to three years, is also important.

7.39 In Sri Lanka, regular visits from technicians during the first year helped train families to use their systems properly and to learn effective load management practices. User education should be directed at the persons in the households responsible for the routine maintenance. These are generally older children or women. Women and children typically derive greater benefits than men do from the solar home systems. They are willing and interested in taking a proportionate share in caring for their systems. In many countries, children from the ages of 11-15 are also those household members most interested in the technical aspects of the solar home system and are therefore more likely to understand the load management principles. To increase involvement of women and children, training should take place in the home whenever possible, preferably with the installation team or technician providing information based on materials and guidelines supplied by the vendor. Solar home system programs also afford excellent opportunities to train women for both administrative and technical positions.

7.40 In summary, technical performance is key to the long-term sustainability of a PV household electrification program. Consumers need well-designed, properly assembled, and correctly installed products that are affordable and fit their budgets. Overselling must be avoided. Spare parts should be easily available as well as local, appropriately trained technicians to provide maintenance and repair services. User education should target those members of the household most affected by the system and best able to perform routine maintenance tasks.