Solar power for the poor: facts and figures

By: David J. Grimshaw and Sian Lewis

Solar power could help alleviate rural poverty.戴维·J·格里姆肖（David J. Grimshaw）和西安刘易斯shine a light on its progress, potential and pitfalls.

Increasing access to energy is critical to ensuring socioeconomic development in the world's poorest countries.

An estimated 1.5 billion people in developing countries have no access to electricity, with more than 80 per cent of these living insub-Saharan Africa或者South Asia. [1]

这个问题在偏远地区最为严重：撒哈拉以南非洲农村地区有89％的人没有电，这是城市地区比例的两倍以上（46％）。[1]

For these people, even access to a small amount of electricity could lead to life-saving improvements in agricultural productivity, health, education, communications and access to clean water.

Options for expanding access to electricity in developing countries tend to focus on increasing centralised energy from fossil fuels such as oil, gas and coal, by expanding grid electricity. But this approach has little benefit for the rural poor. Grid extension in these areas is either impractical or too expensive.

Neither does this strategy help tackleclimate change. Power already accounts for 26 per cent of global greenhouse gas emissions and while most of this comes from the developed world, by 2030 developing countries are predicted to use 70 per cent more total annual energy than developed nations.[2]

这re is therefore a clear need for pro-poor, low-carbon ways to improve access to electricity in the developing world — solar power could be one such solution.

Place in the sun

地球是ceives more solar energy in one hour than the world population consumes in an entire year.

Almost all developing countries have enormous solar power potential — most of Africa, for example, has around 325 days of strong sunlight a year, delivering, on average, more than 6 kWh energy per square metre a day (see Figure 1).

这Desertec Foundation, a joint German and Jordanian company, estimates that covering just one per cent of global deserts in solar panels could power the whole world. [3]

图1：潜在太阳能的世界地图（kWh/m2/day中的太阳能显时发生）（credit: Hugh Ahlenius,UNEP/网格 - 启示地图和图形库).

And yet the countries that receive the most solar energy are often also the ones least able to benefit from it, due to a lack ofknowledge和capacityto harness solar power and convert it into electricity.

这technology

这re are two ways of using power from the sun: collecting its heat (solar-thermal) or converting its light into electricity (photovoltaics).

Solar-thermal devices use 'collectors' — ranging from flat plates put on roofs to parabolic dishes, power towers or solar pyramids used in solar power plants — to absorb sunlight and produce heat.

太阳能设备最简单地用于加热或冷却，但也适用于干燥作物，巴氏杀菌或烹饪（见表1）。

Through concentrating solar power (CSP) systems, that use a combination of lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam, they can also be used to provide electricity. The concentrated sunlight heats water to produce steam to drive a turbine, connected to a generator.

Solar photovoltaic (PV) systems use solar cells, linked together in 'modules' (solar panels), to convert light into electricity. They range from a few small cells that can run a calculator to huge solar power stations with thousands of solar panels.

More than 90 per cent of PV systems are based on silicon materials. PV systems that are connected to the electricity grid include a device called an inverter to turn the direct current (DC) power generated by solar panels to the alternating current (AC) power used on the grid.

Off-grid PV systems may also include an inverter but also require batteries to store surplus energy, and an electronic charge controller to prevent the batteries from overcharging.

At present, solar-thermal systems are about 30 per cent efficient at turning heat into electricity — compared with approximately 15 per cent efficiency for PV systems. But, in the long run, the development of newer materials for PV systems, such as polymers and nanoparticles, should increase their efficiency.

Rising interest

Neither solar-thermal nor PV are new technologies, but they are not widely used to generate electricity because, compared with carbon-based energy supplies, they remain relatively expensive.

国际能源机构估计,我n 2007, solar PV and solar-thermal contributed less than 0.2 per cent of gross global electricity production. [4]

然而，随着化石燃料成本不断上升，对供应的关注越来越大 - 一些分析师表明，我们早在2025年就可能已经用完石油了，并提高了人们对化石燃料在气候变化中的作用的认识，市场条件将越来越有利于太阳能。政府补贴也可能有助于鼓励太阳能的增长。

当然，在过去的五年中，对太阳能的兴趣激增。2008年，太阳能的新金融投资总额为335亿美元，比2004年投资的6亿美元增长了172％。[5]太阳能PV产能同样令人印象深刻，2004年至2008年之间增长了6倍，达到2008年。达到超过16GWH（见图2）。[6]

Figure 2: Global capacity in solar PV from 1995–2008. Source:Renewable Energy Policy Network for the 21st Century [6]

Interest should rise further as technologies improve, production scales up and costs fall. The holy grail of solar power economics is to reach grid parity — where the unsubsidised cost of solar power is equal to, or cheaper than, the cost of conventional grid electricity.

Analysis bymanagement咨询公司McKinsey＆Company预测：“到2020年，至少有十个阳光强的地区将达到电网均等”。[7]但是这些几乎肯定会在意大利，日本，西班牙和美国等发达国家内。

And for developing countries, even once grid-parity is reached, off-grid solutions will still be required to deliver power to remote communities.

While the cost of large grid-connected solar systems will fall as solar panel prices drop, smaller off-grid systems are unlikely to see similar cost savings, partly because the price of batteries will remain high.

电池可占离网太阳系成本的40％。而且要替换它们的额外费用，因为电池不太可能持续到太阳能电池板。

电器的效率还可以对通过离网太阳能系统供电的成本产生巨大的影响。

For example, one German engineer, with experience in taking PV systems to developing countries, estimates that the cost of supplying off-grid solar electricity to a single village would drop from US$35,000 to just US$8,300 if the village separately installed energy efficient compact fluorescent light bulbs and newer model refrigerators and computers. [8]

Solar home systems

农村设置中最常见的太阳能光伏系统是太阳能系统，由太阳能电池板组成，连接到电池和电荷控制器。它通常包括至少一个光和一个插座，可为其他电气设备（例如收音机，电视或手机充电器）供电（见图3）。

图3：太阳能家庭系统组件。来源：Household Energy Network

到2007年，发展中国家有超过250万所房屋可以从太阳能家庭系统中获得电力。[9]

Growth in solar home systems has been particularly strong in Asia — most notably in Bangladesh, China and India — where microfinance schemes or government and donor support has facilitated access.

In 2008, the World Bank approved two projects in Bangladesh to install 1.3 million solar home systems. And its China Renewable Energy Development project, which closed in mid-2008, installed more than 400,000 solar home systems in northwestern China. [6]

In Africa, the rise in solar home systems has been slower. But by 2007, the continent still had more than 500,000 systems in use, more than half of these in Kenya and South Africa. [9] Most projects in rural Africa outside these two countries are relatively small.

For example,Zara Solar Ltdis a small solar business that sells solar PV systems to rural communities in Tanzania. Set up by a local entrepreneur, the company has received support from several donors, including the World Bank, Lighting Africa and the Ashden Awards for sustainable energy, and has installed more than 4,000 solar systems in northern Tanzania.

尽管资本支出很高，电池和维护成本持续，但离网太阳能系统可以节省资金。考虑到正确的融资机制，Zara Solar Ltd客户可以在不到两年的时间内偿还太阳能家庭系统的费用。

太阳能系统还可以为学校或农村卫生诊所等公共建筑供电。这Solar Electric Light Fund, for example, supports the installation of hybrid solar–diesel systems — that generate more than 90 per cent of their electricity from the sun — to power health clinics in several countries, including Burundi, Lesotho, Rwanda and, most recently, in Haiti, following the devastating earthquake in Port-au-Prince in January 2010.

Light at night

In many cases, clean good quality light can be provided with very little electricity — and low cost — with a huge impact on quality of life.

Most villages in Africa, Asia, and Latin America rely on kerosene lamps and candles for their lighting. These cost the average household US$40–80 each year, emit pollutants that pose serious health risks, including respiratory or eye infections, kidney and liver problems and can cause house fires that kill people.

Solar lamps offer a safer, cheaper alternative. Indian companyNEST Ltdmakes solar lanterns that are small, practical and cost just US$35 each. They can be paid for in instalments over one to two years, from savings on kerosene. More than 100,000 houses in the states of Andhra Pradesh and Maharashtra use NEST lanterns, saving more than 20,000 tonnes of carbon dioxide each year. [10]

去年，IEEE Spectrum报道,丹麦RisøNational Laboratory for Sustainable Energy had developed a "potentially life-saving lamp" using light emitting diodes (LEDs), PV cells and ultra-thin lithium batteries. [11]

It is a flexible sheet of PV cells that, when you clip the corners together glows with reading quality light.

这prototypes cost US$27 per lamp and last for about one year. The development team are confident that costs can be reduced to US$7 — perhaps even half that if they outsource production to China — which would offer a significant advantage in both cost and health for local people.

Indeed, solar energy is increasingly being used in a wide range of off-grid applications. (see Table 1).

Application	Technology	How it works	Benefits	Example
Solar vaccine refrigerator	PV panels + lead-acid batteries	Solar panel provides electricity to power fridge; batteries store it to ensure continuous operation.	Reduces reliance on harmful kerosene; extends life of vaccines.	KXN Nigeria Ltd has installed more than 189 vaccine solar fridges in northern Nigeria.
Solar water disinfection (SODIS)	Sunlight + plastic PET (polyethylene terephthalate) bottles	Exposure to UV sunlight destroys pathogens and bacteria.	提供洁净水的来源; reduces waterborne diseases.	More than 1.4 million people use SODIS in Asia; 360,000在拉丁美洲使用； more than 340,000 use it in Africa
Solar pasteurisation	Solar cooker (see below) + water pasteurisation indicators (WAPIs)	Solar cooker heats water and WAPI (small tube/capsule containing wax that melts at 65°C — the temperature at which viruses and bacteria are killed) indicates when it is safe to drink.	节省燃料； reduces waterborne diseases.	Adventures in Health, Education & Agriculture Development (AHEAD)在坦桑尼亚，已经为100,000多人带来了太阳能化。
Solar water pump	PV panel + electric motor	Solar panel drives electric motor which powers pump to feed water into reservoir/storage tank.	Provides water for domestic use or irrigation; saves labour.	More than 10,000 solar water pumps in use worldwide; [12] Research in Benin shows solar pumps for drip irrigation improved diets and incomes [13].
太阳能食品干燥机	Box with glazed cover and vents + mesh racks	Food is placed on mesh racks and dried as sun heats box.	减少化石燃料的使用； reduces contamination; 减少收获后的损失	Fruits of the Nilein Uganda buys fruit from small farmers and uses solar driers to boost incomes of about 1400 people.
Solar electric fencing	PV电池 +电源调节器 +电池	PV cells charge battery, which provides DC voltage to 'live' wires in the fence.	减少动物突袭； protects livestock and crops.	Community Markets for Conservation (COMACO)has installed solar fences in Zambia, protecting crops for more than 1500 families.
太阳WiFi	PV panel + wifi router and antenna + battery + charge controller	Solar panel charges battery to power wifi antenna and router that 'hop' Internet signal from single broadband access point across multiple nodes.	Increases Internet access; decreases digital divide.	Green Wifihas set up wifi networks for schools in Panama and Senegal.
Solar phone	PV solar charger integrated into mobile phone; 或者solar panel + electric sockets	PV cells charge battery within phone; PV电池将电池充电到电源插座。	Improves rural communications; provides livelihoods (via charging stations).	Digicel distribute solar phones in Haiti and Papua New Guinea; Safaricom sells solar phones in Kenya; Ericsson has installed 12 village charging stations in Millennium Villages across Africa [14].
Solar radio	PV面板 +无线电收发器 +电池	Solar panel powers batteries for transceiver.	Improves rural communications; reduces transport costs; if connected to a laptop, also increases access to online information and advice.	Freeplay Foundationhave distributed more than 10,000 solar radios to provide information and advice on health, agriculture and environment; 这Madrid Association of Engineers without bordersuses solar radios to support health services for 50,000 people in rural Peru.
Solar cooker	Solar thermal: heat-trap boxes, curved concentrators, panel cookers	镜子或反射金属等设备会将光和加热到小烹饪区域。	Reduces reliance on traditional fuels such as wood or charcoal; reduces indoor pollution.	Solar Cookers Internationalsupports solar cooker businesses across Africa, and has donated solar cookers to thousands of families in refugee camps in Chad, Ethiopia, Kenya and, most recently, Haiti.
Solar water heating	Solar thermal collector + water storage tank	收集器加热通过它的流体，并将热量储存在水箱中。	Reduces reliance on traditional fuels; 减少碳排放和局部污染。	In Rizhao, China, 99 per cent of homes use solar water heaters.

Table 1: Off-grid applications of solar power

Solar energy is also being used to bring other benefits — in many cases, it can provide the first step out of poverty by providing new skills and sources of income.

For example, the nongovernmental organisation太阳能援助机构trains entrepreneurs in developing countries in business planning and market research to help them set up small solar businesses to convert kerosene lamps into solar lanterns and build solar chargers or solar radios from local materials.

Similarly, the nongovernmental organisationBarefoot Collegetrains 'Barefoot Solar Engineers' (mostly from rural villages in Africa and Asia) to install, repair and maintain solar lighting units in an effort to promote rural solar electrification and boost incomes for poor villagers.

By the end of 2009, the college had trained 461 solar engineers, including 211 women and, according to the college benefited an estimated nearly 900,000 people.

Finance and beyond

But improving access to solar power for the rural poor in developing countries still faces a number of hurdles.

Beyond thepolicyenvironment, which favours the development of fossil fuels, the most significant isfunding.

Access to solar power is either purchased in the open market or provided through international aid.

这re are a wide range of aid models in operation. Large donors such as the World Bank and the International Finance Corporation are major funders of solar PV in the developing world, supporting projects in Africa, Asia and Latin America valued at more than US$600 million.

Specialist organisations such as SolarAid raise money to invest in solar systems for schools or communities with a focus on improving health, education and livelihoods. Manufacturers such asSollatekdonate a number of units to charities per month.

But there is growing interest in moving away from straight aid towards strategies that enable the poor to finance their own energy needs.

For example, microfinance providers, which offer small loans — often based on no collateral — to the poor, are proving vital to overcoming the relatively high capital cost of off-grid solar systems. Many such microfinance providers have been established using funds from major donors, such as the World Bank, but become self-sustaining in the long term through credit repayments.

Those microfinance providers that specialise in selling solar PV systems often include support activities such as training, maintaining equipment and replacing parts, or disposing of damaged batteries.

For example,Grameen Shakti, a microfinance provider in Bangladesh, has installed more than 320,000 solar home systems based on microcredit in the past decade and aims to increase this number to one million by 2012. It has trained more than 4,400 technicians (mostly women) and set up 45 'technology centres' to install and maintain solar systems locally.

Microfinance providers can include charitable foundations, such as theSolar Energy Foundation在埃塞俄比亚安装了2000多个太阳能家庭系统。

Banks may also offer microfinance. TheAryavart Gramin银行in India, bulk-orders PV systems and provides purchase, installation and maintenance loans to rural customers. The credit repayments are cheaper than the monthly cost of kerosene and can be paid back over five years.

Private solar businesses can also help in microfinance. The Indian companySELCO, for example, has sold more than 100,000 solar home systems in the past 13 years. While it doesn't make loans itself, it helps connect customers with microfinance providers, in many cases providing a 'down-payment guarantee' to help cover upfront capital payments.

Governments should also take a role in making solar financially affordable — by supporting the system that gives the poor access to solar technology.

This means investing in research and development for the technology itself, and using a system of subsidies to improve uptake of solar power and to support installation and maintenance costs.

To ensure the benefits are felt by the rural poor in remote communities, such subsidies must favour decentralised, off-grid, small solar systems over centralised, fossil fuel-based solutions.

Beyond financing, there are other hurdles to improving access to solar power for the poor. These include improving local ownership of solar technologies, weaving off-grid solar systems into climate change policies and targets for reducing global emissions, and scaling up production technologies to reduce capital costs.

这bottom line is that scaling up solar power for the poor will depend on a mix of scientific improvements, policy initiatives, and collective action aimed at tackling climate change and electricity poverty.

戴维·J·格里姆肖（David J. Grimshaw）is head of Practical Action's international programme in new technologies and senior research fellow in emerging technologies at the UK Department for International Development.

西安刘易斯is commissioning editor at SciDev.Net