Introduction

Energy is an essential part of modern life but many people in the world, especially the poorest people living in developing countries, do not have access to adequate energy resources. They may have no centralized electricity or the supply may be erratic and unreliable. This is why decentralized power delivery is needed, whether provided through modern technologies such as solar photovoltaic panels or through more traditional technologies which can be improved to deliver better performance, such as charcoal production.

In the domestic setting in developing countries energy is primarily used for lighting, cooking and heating, and to power small appliances such as radios. Families that can acquire more efficient sources of power will have a better living environment. Solar lighting can replace kerosene lamps, making the home lighter for longer as well as safer and cleaner. Despite the initial costs, replacing older forms of power generation can ultimately save money for families who would otherwise be spending money on fuel on a weekly basis. Access to energy enables people to undertake income-generating activities that would otherwise not be possible. Even small amounts of energy can make a big difference in people's everyday lives and in the amount of money they can earn.

In rural areas energy is needed for agriculture and crop processing. Energy for water pumping helps to increase crop production through improved irrigation. Small-scale milling or grinding equipment can greatly improve the income of farmers and allow farming families to have some control over how they manage their crops. Powered oil-expelling equipment will increase the processing capacity.

Energy is not only required for agriculture; urban areas need energy and often do not have sufficient supplies. Small businesses and shops need energy. Hairdressers in Kenya make the most of the energy delivered through renewable sources to improve their service to customers and help increase their income.

Energy is also needed to power the communication revolution, allowing people to have access to mobile phones which bring a range of benefits, keeping families in touch with one another and improving income generation through better market awareness by allowing people to know the best time to sell their produce and where the best resources can be found.

In schools, electric lighting and computers help children learn, with access to the internet providing them the opportunity to know more about the wider world. Hospitals and health clinics cannot function effectively without energy. Importantly vaccines must be refrigerated to ensure they remain effective.

Although centralized energy delivery is growing in almost every part of the world, there remains a large unmet demand for energy and delivery is very uneven. Grid connection will not reach sufficient numbers of people in forthcoming years and supply from centralized grid systems will remain unreliable as demand outstrips supply. Decentralized energy delivery has the advantage that it can spread rapidly to remote areas and is economically more attainable. This means that the technologies described in this publication will be suitable for the many people who will otherwise be unable to access an energy supply.

This book brings together a selection of the technical briefs produced by Practical Action on the subject of energy. The work of Practical Action and others has been to enable people living in poverty to improve their living standards. One way of doing this is by improving access to energy. Small-scale renewable energy technologies are a practical way of delivering clean energy to rural populations, providing energy for lighting, radios and other small domestic appliances as well as supporting economic activities that will improve incomes. Access to energy can also be a driver for poverty reduction by enabling businesses to develop and production to grow. This may be through a village-scale initiative, such as a micro-hydro scheme which could supply energy to many people and their businesses through a mini grid, but it also includes standalone systems that are used by one household independently.

Not only do clean energy technologies improve the lives of people, they also help reduce environmental pollution by replacing fossil fuels. Consequently, some small-scale renewable energy projects have been financed by carbon credit schemes.

Solar energy

Solar energy can be captured in two ways. The more traditional approach is to capture heat using some sort of thermal device such as solar water heater, while the other is to generate electricity directly through the use of photovoltaic panels.

Solar photovoltaic energy is ideal for household systems or isolated applications such as solar water pumping. These systems are relatively easy to transport and install, and require very little operation and maintenance. Although running costs can be very low, for many people solar photovoltaic technology is still an expensive option in terms of the initial capital cost. However, solar photovoltaic technologies have been falling in price over the past few years and are likely to continue to fall even further in coming years. The price of solar panels fell by almost 50 per cent in 2011 according to Bloomberg New Energy Finance (BNEF). The overall cost of solar electricity is now cheaper than that produced by diesel generators when looking at periods of seven years or longer.

The falling cost of solar photovoltaic technology components is mainly a result of the economies of scale arising from increased production, rather than any radical changes in the technology. Commercial panels still only convert 15 to 18 per cent of the energy that reaches them, but this low efficiency is relatively unimportant compared to the cost. This reduction in cost means that the technology is becoming available to poorer households.

Small-scale solar thermal energy options are also discussed in this publication, concentrating specifically on solar drying and solar distillation. Solar thermal energy has some significant advantages over the more technologically advanced PV systems in that the initial investment can be very small and the running costs are also minimal. The technology can be manufactured locally on a small scale. However, many small-scale solar thermal energy technologies have not dramatically changed over the years and have, to some extent, been relatively neglected in comparison to the developments in solar PV. Solar water heating is perhaps the most widely used solar thermal technology. It has become common in some regions such as the Mediterranean and North Africa, while not much used in other regions. To a lesser extent solar water heating has progressed in a similar fashion to solar PV in that it has developed and expanded in its use with steadily increasing production and thus reducing in cost. The technology is suitable for small-scale local manufacture.

Other solar thermal technologies include solar food drying, which Practical Action has promoted over many years. Fruit and herbs can be dried and sold in the off season, helping to bolster the farmer's income.

Micro hydro and river turbines

Micro-hydro schemes are usually installed at the village level, so that one scheme provides electricity to many homes and to industries within the village. The investment needed for a micro-hydro scheme is large compared to household income, so financial structures play an important role in the implementation of micro-hydro schemes. Keeping the cost down to a realistic level is an important factor in making this technology viable. Cost can vary considerably depending on the physical locations and the terrain of the site. Smaller sites tend to be more expensive per kilowatt of power delivered and cost tends to increase as the head (i.e. the height that the water will fall through) decreases.

Micro hydro has a significant history in some regions of the world, while in other parts its potential has not been realized. The technology is well proven and reliable. Experience is being gained in new regions of the world, especially in Africa where small-scale community hydro is beginning to establish a firm footing.

River turbines are different from conventional hydro schemes in that there is no head of water. Instead the energy in the flow of the water is used to power a turbine in a similar way to air flow in wind turbines. This technology is not widely used but they have been of increasing interest not only for developing countries but also as part of the energy solution for industrialized countries. Practical Action has developed this approach in Peru while larger systems have been developed in North America and Europe. The technology is closely related to those used to harness tidal energy.

Biomass, biogas, and biofuels

Biomass as a solid fuel includes a range of materials. Most familiar is wood used for cooking in many households, while others use crop residues such as rice husk either as fine residue or made into briquettes. Processing is very important and small changes to traditional approaches can provide significant improvements in quality and quantity.

Biomass is used in one form or another by the majority of people in the world, primarily as a fuel for cooking either as wood or as charcoal made from wood. However, there are many options in the use of biomass and significant research has been undertaken in some areas of biomass processing, especially in the production of liquid biofuels that can be used to replace fossil fuels. Although large-scale biofuel production has generated controversy because it competes for land that would be used to produce food, small-scale biofuel production can offer local producers some significant benefits.

Charcoal production is done in many parts of the world on an informal basis and charcoal is widely used in urban areas as a cooking fuel. Improvements to the basic approach to production can significantly reduce emissions and improve the output of the kilns. In recent years there has been interest in developing charcoal production using crop waste and invasive plant species as a fuel source instead of wood. This is highlighted in Sudan where mesquite has become a real problem, but can be used to produce charcoal which is sold in the cities.

Liquid biofuels include a range of substances such as biodiesel and bioethanol. The expansion of liquid biofuels has been rapid in recent years and will likely continue to rise as attempts are made to replace fossil fuels. Large-scale operations are controversial because they occupy land that has the potential to produce food crops. Small-scale biofuel operations have less controversy associated with them and can make a positive impact for communities in developing countries Biogas has been promoted over a number of years and can work well supplying energy to homes for cooking and lighting. It can also be used to generate electricity if the supply is sufficiently large. It has the advantage of providing a means of managing waste materials in sanitation sites. Bio-sanitation is of great interest as a sanitation solution in many locations, especially in urban areas where more simple toilets requiring more space or regular emptying can be substituted.

Energy for rural communities

The issues surrounding energy in rural communities are not just about the fuels that are available but also how to make best use of them and what they can be used on. Small-scale energy supplies to domestic homes will be used for lighting and cooking; in some colder regions heating will also be important. Small appliances such as radios are popular along with mobile phone charging.

Away from the domestic setting, energy is needed for schools and health centres where computers or refrigeration for vaccines require a reliable energy supply. Energy can also be used to generate income. Micro-hydro schemes have prompted the development of small-scale industry as a way of making use of the energy available in daylight hours, when domestic use is at its lowest.

Delivering electricity to more remote households is a challenge that is often regarded as too difficult or costly to achieve, but there are low-cost options available which are looked at within this book. However, it is not only electrical energy that needs to be considered. Often there will be competing energy options that can potentially be used so it is important to be aware of how these can be used and what the relative merits are. Two areas where this can be seen are food preservation, where options include coolers and refrigerators, and lighting, where options range from candles to modern light-emitting diode systems.

About Practical Answers

Practical Action has worked on providing information on appropriate technologies throughout its existence and one aspect of this is Practical Answers, its technical information service. The service aims to provide information and understanding about a wide range of low-cost appropriate technology options that can be used to help people move out of poverty. It covers such diverse topics as agriculture, low-cost construction, disaster risk reduction, food processing, water and sanitation, small-scale manufacturing and production, transport, waste management, as well as energy technologies covered in this publication and others that have not been included such as wind technology and improved stove design – although these subjects are discussed in Chapters 8 and 15 (wind), and Chapter 11 (stove design).

Technical briefs, manuals and other formats such as videos and audio files have been produced to help guide people to make technology choices and find the best route to better lives, either directly or through intermediaries such as development charities like Practical Action. This information is available through the Practical Action website, on CD, and in print. Individuals can also make direct enquiries to any of the Practical Action offices on any of these technical subjects. Questions can be submitted free of charge to any office where Practical Action can call upon its staff and partners to provide an answer that will be as relevant as possible to the particular circumstances.

This book has been produced as a collaboration between Practical Answers and Practical Action Publishing, to make Practical Action's technical information on energy available in printed form. It covers just some of the energy technologies that Practical Action (or, under its previous name, ITDG) has been working on over the years, and providing information on through its technical information service. The subjects included in this book have consistently been of interest, although the technology has developed over the years. These changes have been reflected in the document revisions.

Some well-established small-scale technologies such as hydro and solar have been included here, along with examples of how energy can be effectively used for such things as lighting and refrigeration. Topic areas such as wind power and stoves that have not been described in detail in this book are covered in other publications, and each chapter includes a bibliography where further reading is listed. Readers who are interested in finding out about other technologies can look at the Practical Action website (http://practicalaction.org/practicalanswers/).

Solar photovoltaic energy

This chapter explains solar photovoltaic technology and provides some context to its use in developing countries, looking at the main components and at issues of cost. The different types of panels that are commercially available are outlined and how these are incorporated into a typical solar system. Typical applications for developing countries are presented, and the potential for local assembly and dissemination.

Keywords: solar, renewable, photovoltaic, hybrid systems, photovoltaic applications

Introduction

Photovoltaics (PV) is a technology that converts sunlight directly into electricity. It was discovered in 1839 by the French scientist Becquerel, who detected that when light was directed onto one side of a simple battery cell, the current generated could be increased. In the late 1950s, the space programme provided the impetus for the development of crystalline silicon solar cells; the first commercial production of PV modules for terrestrial applications began in 1953 with the introduction of automated PV production plants.

Today, PV systems have huge value in areas remote from an electricity grid where they can provide power for water pumping, lighting, vaccine refrigeration, electrified livestock fencing, telecommunications and many other applications. With the global demand to reduce carbon dioxide emissions, PV technology is also gaining popularity as a mainstream form of electricity generation. Millions of solar PV systems are currently in use worldwide, with an installed capacity of 40 GW globally by the end of 2010 (REN21, 2011), yet this is a tiny proportion of the vast potential that exists for PV as an energy source.

Photovoltaic modules provide an independent, reliable electrical power source at the point of use, making PV particularly suited to remote locations. However, solar PV is increasingly being used in homes and offices for electricity to replace or supplement grid power, often in the form of solar PV roof tiles. The daylight needed is free, but the cost of equipment can take many years to achieve payback. However, in remote areas where grid connection is expensive, PV can be the most cost-effective power source.