The Experience of ULOG with Small Scale Projects Promoting Solar Box Cookers and Scheffler Reflectors

Michael Götz, Rolf Behringer, Alec Gagneux, Françoise Hänggi, Heike Hoedt, William Illboudo, Christine Lippold, Alexandra Meuwly, Ulrich & Liesel Oehler, Wolfgang Scheffler

Correspondence address: Michael Götz, ULOG Suisse Romande, Rue Matile 71, CH-2000 Neuchâtel, Switzerland


Phone and fax: 0041 / 32 / 725 38 16


For the last 15 years, the ULOG group has been promoting solar box cookers and ‘Scheffler-type’ parabolic cookers in developing countries and within Europe. The ULOG group is a ‘loosely organised’ NGO which concentrates mainly on small-scale (and low-cost) projects. Over the years, the following factors have crystallised as being central for the success of a project: Personal interest of local project managers, focus on the use as well as on the construction of the technology being introduced into a new area and long-term project follow-up. Short-term projects of ‘development tourism’ nature have a high probability of failure.


About the ULOG group

The ULOG group was founded by Ulrich and Lisel Oehler in 1984 after they had been introduced to solar cookers in Botswana. In the years that followed, the engineer, Ulrich Oehler, developed a full range of solar box cookers under the name of ULOG. In 1987, the Austrian physicist, Wolfgang Scheffler, joined the group with the aim of developing larger parabolic cookers. Since then and for more than 15 years, the ULOG group has been promoting solar box cookers and ‘Scheffler-type’ parabolic cookers in developing countries and within Europe [1].

The ULOG group is a ‘loosely organised’ NGO which concentrates mainly on small-scale (and low-cost) projects. Whereas the members of the group organise their projects in a rather independent manner, they do have a ‘headquarters’ in ‘Basel/Switzerland’. Regular meetings are held to discuss project work and technical issues.

The ULOG solar box cooker

The ULOG solar box cookers are amongst the more solid box cookers available. ULOG cookers are not as cheap as cardboard ‘panel cookers’, but they can be built with material which is available in most countries (wood, glass, natural fibres, recycled aluminium sheets from printing shops i.e. offset-sheeting) and they have a long life-span. A solar box cooker can be used for both cooking and baking. There are different models ‘cooking’ for one to 10 people. Thousands of construction plan copies circulate in many countries around the world and there are even companies selling ‘ULOG clones’ over the internet.

The Scheffler community kitchens

Scheffler community kitchens are a more powerful and a more technical approach to solar cooking than the box cookers. A reflector constructed of many mirrors or polished aluminium facets bundles the sunlight into a focal area inside the kitchen. A sophisticated design allows the fixed-focus to be inside the kitchen, whereas the fixed stand of the reflector is outside the kitchen. A mechanical clockwork (made out of bicycle parts) or a photovoltaic motor turns the reflector to follow the movement of the sun. The cook has only to set the position of the focal point in the morning and then he can work all day inside the kitchen. The most common model of Scheffler reflectors is the ‘S280’ with a power of up to 3 kW for a pot size of 50 to 70 litres.

Fig. 1. A ULOG solar box cooker.

Fig. 2. Principle of the Scheffler parabolic reflector.

Promotion and information work in Europe

It is an important part of ULOG’s philosophy to not only teach ‘appropriate technology’ to people in developing countries, but also to make this technology part of our lives. We are convinced that for solar cookers to be widely accepted they have to overcome the image of a ‘poor mans tool’. This will only be possible if the technology is also utilised in rich industrialised countries. For this reason, we promote solar cooking in central Europe. We teach people to build and use their own cookers. During the summer months, we organise solar cooking demonstrations. Information work is done through as many channels as possible.

Project work in developing countries

ULOG’s senior experts organise their projects in a rather independent manner, but always in collaboration with a host organisation within the project country. The project leader is responsible for preparation, execution and fund-raising. (An important sponsor of projects in developing countries is the Swiss organisation ‘GloboSol’ [2]). The ULOG expert normally stays between 2 weeks and 6 months on location. Most projects demand repeated visits - usually once a year. The personal contact and friendship between ULOG members and the local managers is part of our success.

Before starting a project, several points need to be clarified. The following list is to be seen as a guideline. (For initial contact in a new region, the points are not implemented in a stubborn manner).

* The host organisation should show a strong interest in solar cooking and it should have definite plans to continue production and implementation of the cookers. A local manager should be designated responsibility over the project.

* The technical infrastructure should be suitable for the production of the cookers (particularly of importance for Scheffler reflectors).

* The host organisation, as well as the future users of the cooking units, should be motivated. This may be judged by the willingness of the organisation to pay for material and in their willingness to host ULOG experts. The interest of the users is to be seen in their willingness to pay at least part of the cooker. A free gift has no value!

* An obvious point: the climatic conditions in the region must be favourable for solar cooking (Dry/rainy seasons, sandstorms, ...). Typical local dishes should be tested early in the project, they might be incompatible with the proposed cooking solution.

* The users (cooks) must be involved in the project and their wishes respected where possible.

The last point is perhaps the most important lesson we have learnt over the last years: Solar cookers (at least the more technical models) and their fabrication often interests men, but most of the cooking is done by woman. Learning to cook with a solar cooker, however, is even more important than learning to build one - this holds especially for the easy-to-build box cookers. It is usually of benefit to include local woman’s groups into the project.

As ULOG experts are free to organise their projects in their own way, there is room to combine the rather technical topic of solar cooking with education about more general topics (holistic project approach). Birth control, impact of globalisation, gender issues, organic agriculture and other appropriate topics may be discussed.

Case studies:

In Burkina Faso, a small family enterprise (ISOMET) started the production of solar box cookers in 1996. The project is supervised by a member of ULOG and the oldest son of the family, who at present is studying in Germany. Due to the personal interest and the perseverance of the family members, ISOMET is expanding successfully. Climatic conditions allow the use of the cookers and the female family members have gained extensive experience in cooking local dishes.

In Sumatra/Indonesia, the local catholic church invited an ULOG expert to teach the production of solar box cookers in their carpentry school. There was no problem in manufacturing the cookers and the local students, as well as the hosting church members, showed a lot of interest in the topic. Nevertheless, the project was not successful: The focus was on production, not on the utilisation of the cookers. The host organisation showed no intention of using the cookers in the church kitchen, the cookers were meant for the ‘poor locals’ only.

The production of Scheffler reflectors in India is the largest project, where members of ULOG and its German partner organisation ‘Solare Brücke’ are involved. A local ecological centre (ICNEER) started production of Scheffler reflectors a few years ago and is now selling many units every year. Reflectors built by ICNEER were used for the world’s largest solar kitchen in Mount Abu (owned by the Brama Kumaris World Spiritual Organisation). The success of this project is based on two aspects: the personal engagement of the couple leading the eco center and the follow-up of the inventor of the reflectors over several years.

The worst case is described here as a means of example and as a warning: An enthusiastic person with a great amount of goodwill calls ULOG in order to learn how to build a box cooker - one week before leaving for a short visit in a Southern country. The wonderful news of solar cooking is to be introduced to the locals before even the first local meal has been cooked. In many cases, the enthusiastic person has never even used a solar cooker themselves. Many solar cooking ‘projects’ of this type have led to unused cookers and to a bad image of solar cooking within many development organisations.

Conclusion: Small projects have a chance of success as long as they are prepared seriously, as long as several conditions (as discussed above) are fulfilled and the follow-up is not neglected. Short projects of ‘development tourism’ nature, however, have a high probability of failure.


[1]Ulrich Oehler, Wolfgang Scheffler, Solar Energy Materials and Solar Cells, 33 (1994), p. 379-387