Reference no: EM133274777

Problem:

Compared to open field cropping, greenhouse cultivation has higher crop yield and quality but also higher energy use and environmental impacts per unit land area. Which TWO of the following are the major factors that contribute to energy consumption and carbon emission in the controlled environment system?

a. Greenhouses are responsible for a great percentage of carbon emissions since they are mostly run on fossil fuels

b. The majority of current greenhouses utilizing conventional materials and traditional technologies cause high constructional and operational cost

c. The greatest heat loss in greenhouses arises from glazed areas. Almost all of greenhouses use plastic or glass which have high transmissivity, but poor overall heat transfer coefficient

d. Conventional facade materials (glass, polyethylene, semi-rigid plastic, and the plastic film) have very high shading coefficients, resulting to remarkable solar heat gains in summer, and insufficient thermal resistance values causing notable heating demand in winter