Beschreibung
In its continuing efforts to improve production and storage, European agriculture and food industry consumes ever more energy. Hence, as was the case for all European sectors founded on intensive energy consump tion, agriculture was also severely affected by the shortages and price increases of conventional energy sources over the past decade. The energy consciousness generated in this way led to a widespread con sideration of the application of other, renewable energy sources. The potential applications in agriculture are, however, extremely diverse, and this explains to a great extent the fragmentary nature and even in some cases the mediocre level of current research. The objective of this book is, therefore, to guide the reader in a syste matic way through the apparent chaos of operational data which are currently available on the subject matter: thermal applications within agriculture of solar energy by means of solar collectors, passive designs and storage devices. While in volume I of this series H this area is assessed from a more general economic perspective, this tome II takes a more detailed technical approach. The results of this book were produced in the form of a European concerted action under the leadership of the Commission in Brussels. All possible data were collected by national representatives in the EC member countries. Coordinators were Professor V. Goedseels and Mr E. Van der Stuyft from the Katholieke Universiteit Leuven and Professor G.
Autorenporträt
InhaltsangabePreliminary notions.- - Preliminary notions.- 1. Fundamental criteria for a successful solar application.- 2. The (thermal) energy demand in agriculture.- 3. Solar radiation in the European Community - The identification of agro climatic zones.- I Applications of Solar Energy in Greenhouses.- 1: Process requirements - technological options.- 1. Traditional processes.- 1.1. Definition and importance of greenhouses.- 1.2. Production parameters.- 1.2.1. Photosynthesis.- 1.2.2. Respiration.- 1.2.3. Transpiration.- 1.2.4. Nutrition.- 1.3. Parameter dependency and periodicity.- 1.3.1. Light.- 1.3.2. Temperature.- 1.4. Transparent covering materials.- 1.4.1. Greenhouse effect.- 1.4.2. Covering materials.- 1.5. Screens.- 1.5.1. Shadow effect - light reduction.- 1.5.2. Screen materials.- 1.6. Effect of airtightness.- 1.6.1. Humidity.- 1.6.2. CO content.- 1.7. Cultivation techniques.- 1.7.1. Traditional Techniques.- 1.7.2. Nutrient film technique.- 1.7.3. Root zone warming.- 2. Energy conservation.- 2.1. Biological methods.- 2.2. Technical methods.- 3. Solar energy collection and storage.- 3.1. Short time storage (with greenhouse as collector).- 3.1.1. Thermal mass.- 3.1.2. Active short-term storage.- 3.2. Collectors other than the greenhouse itself.- 3.3. Long-term storage.- References.- 2: Present research within the E.C. on the application of solar energy in greenhouses.- 1. Criteria.- 2. Overview of projects on solar energy in greenhouses.- 2.1. Classification.- 2.2. Location of the projects described.- 2.3. Basic Descriptions.- 3. General conclusions for the greenhouse sector.- 3.1. Discussion of the listed research projects.- 3.1.1. Phytotechnical aspects.- 3.1.2. Covering materials.- 3.1.3. Thermal screens.- 3.1.4. Energy storage with greenhouse as collector.- 3.1.5. Energy storage with collectors other than the greenhouse.- 3.2. General evaluation.- Appendix to part I: Some specific research projects on greenhouses.- 1. Evaluation of different covering materials for greenhouse production of strawberries (Belgium).- 2. The biological effects of energy savings in greenhouses (Denmark).- 3. Evaluation of double-covered polythene greenhouse for early tomato production (Ireland).- 4. Comparison of the light transmission of greenhouses covered with twin walled sheets of polycarbonate and acrylic (England).- 5. Monitoring of a greenhouse with helioblocs based on solar energy (France).- 6. Greenhouse climatization by an earth-air heat exchanger (Greece).- 7. Development of a solar system for heating greenhouses (Greece).- II Applications of Solar Energy in Drying Processes.- 1: Process requirements - Technological options.- 1. Drying, why?.- 1.1. The problem: long-term conservation.- 1.2. Drying, a possible solution.- 2. Some aspects of drying process engineering.- 2.1. Characteristics of the drying air.- 2.2. The product.- 2.2.1. The product moisture content.- 2.2.2. Sorption and desorption isotherms.- 2.2.3. The 2 main stages in product drying.- 2.3. The drying set-up.- 2.3.1. Simulation.- 2.3.2. Characteristics of the drying set-up.- 2.3.2.1. Drier types.- 2.3.2.2. Instrumentation.- 3. Requirements and some adapted drying techniques for specific agricultural products.- 3.1. Grain.- 3.1.1. Introduction.- 3.1.2. Requirements in grain drying.- 3.1.3. Description of commonly used grain drying set-ups.- 3.2. Hay.- 3.2.1. Introduction.- 3.2.2. Description of a few commonly found hay-drying set-ups.- 3.3. Fruit.- 4. Evolution and alternative drying techniques.- 4.1. Production cost considerations.- 4.1.1. Energy cost.- 4.1.2. Investment costs.- 4.2. Ecological considerations.- 5. Incorporation of solar energy into the drying process.- References.- 2: Present research within the EC on the application of solar energy in the drying sector.- 1. The main research tracks.- 1.1. The "physical feasibility" track.- 1.2. The "economic feasibility" track.- 1.2.1. Choice of collector type.- 1.2.2. Choice of utilization factor.- 1.2.3. Choice of compo
