Smart greenhouse design and energy pool

AQUATOP: combining optical and thermal characteristics

Aquatop is an innovative symbiosis of a smart cover and an energy pool on top of a greenhouse. Together, these features entail a fundamental rethink of the traditional greenhouse design. The smart greenhouse’s thermal and optical properties can be controlled to suit conditions inside and outside the structure.

Project
With input from Bosvariant and Ideeuwes, DNV KEMA and TNO are developing a new greenhouse concept that allows greater control over growing conditions. The system features a multifunctional water layer on the greenhouse roof, made up of an energy pool to harvest heat and a smart cover for spectral filtration of excess sunlight. With this new concept, the degree of light filtering and hazing can be regulated at all times. The Aquatop R&D project is looking at various possible additives to give the water layer the desired properties. With spectrally selective absorbers added, the water layer will prevent uncontrolled or unwanted heating of the greenhouse. This will have various advantages, including less need for ventilation and reduced CO2 loss. Furthermore, it will be possible to ‘harvest’ energy from the heated water on the roof. The Aquatop will also be capable of acting like a traditional darkening screen: the grower will be able to reduce the total amount of light passing through the roof to prevent over-exposure of the plants. Within the project, particular emphasis is placed on the production of biomass (algae) in the energy pool. The light captured in the energy pool can be converted into heat and/or used to grow biomass. This will then serve as a renewable energy source, helping to meet the greenhouse’s energy needs.

Objectives
The energy pool and smart cover require a fundamental rethink of the traditional greenhouse design. Crop welfare, human safety and light capture will all be focuses of the R&D work. In addition, the socio-economic implications of creating an artificial ‘watery landscape’ on top of the greenhouses will be explored. Aquatop is a clear, visionary statement of ambition for the sustainable greenhouse of the future: a greenhouse that is energy-neutral, economically viable, and in harmony with the watery landscape. The greenhouse of the future will be a sustainable energy source and recreational resource.

The project is divided into three stages
> Light control (technical)
> System design (technical)
> Transformation of the landscape (socio-economic)

The Aquatop concept is a cutting-edge heat exchange technology involving a large area of water and the direct capture of energy in liquid.

Project coordinator
> TNO, the Netherlands

Project partners 
> DNV KEMA, the Netherlands 
> Ideeuwes, the Netherlands
> Bosvariant, the Netherlands

Project details
> EOS-LT (Energy Research Subsidy – Long-Term)
> Duration: July 2008 – June 2011