Solar cooker incorporating CPC type optics and. heat pipe technology description and testing

Manuel Collares — Pereira, Joao Farinha Mendes,

Rita Costa Leal, Jose Pedro Almeida

Departamento de Energias Renovaveis, Instituto Nacional de Engenharia Tecnologia e
Inovagao, Estrada do Pago do Lumiar, 22, 1649-038 Lisboa, Portugal

1 — Introduction

In order to spread the use of solar cookers it would be desirable to provide them with some of the features usually associated with traditional ways of cooking. Actually, in most civilizations, people have some habits which will be hard to change: cooking is usually done inside the house, at any time of the day and conventional fuels can deliver high power to the cooking pan. Common solar cookers must be used outdoors, with the cooking vessel placed on the absorber plate heated by the sun. Besides, there is usually no capacity to allow cooking in the evening, i. e. when the sun is no longer shinning or at the end of the day with the sun low on the horizon when high efficiencies are impossible to be achieved.

With these considerations in mind, a device incorporating Non Imaging Optics (CPC type Optics) and heat pipe technology has been previously developed (Collares- Pereira, 2001). The energy collected by the CPC concentrator was either transmitted straight to a cooking plate for immediate use or stored for subsequent use. The heat pipe allows delivering the energy to the cooking pan, which may be at a certain distance from the CPC collector (for instance inside the house). This solution is also easily adapted to the cooking of larger quantities as is necessary, for instance, in small communities or in schools. In the present paper a new system based on the same ideas is presented. The goal of the new device, presented in this work, is to improve the thermal performance and solve some basic design problems encountered in the previous prototype, bringing us much closer to a potential industrial product.