Development of novel and sustainable cooling technologies for self-sufficient greenhouses and buildings

Project: Applied Research

Project Details

Abstract

Qatar, like other Gulf countries, faces substantial challenges related to the increased demand and intensive consumption of energy for cooling specifically in residential sector and for securing food production. Almost 60% of the electricity is consumed by the residential sector and air-conditioning is the fundamental part of this consumption. On other hand, the production of local vegetables in Qatar has increased from about 50,000 tons during the year before the blockade to about 65,000 tons after the blockade corresponding to an increase of about 30%. The total area of protected greenhouses increased from 49 hectares in 2007 to 73 hectares in 2018. It is important to note that the Ministry of Municipality and Environment (MME) in Qatar has recently announced 34 new strategic projects for private investors to produce vegetables using greenhouse technology with an area of about 100,000 m2 per project. Energy consumption in greenhouses accounts for 50% of the cost of greenhouse production and the fundamental energy consumption (cooling or heating depending on the region) could comprise more than 90% of the total energy consumption in a greenhouse. Qatar is dependent on natural gas-based electricity generation, causing considerable environmental emissions. In addition, there is a very high cost associated with cooling due to the high electricity consumption. Therefore, there is an obvious necessity to design and develop sustainable, smart, novel, efficient and environmentally friendly cooling techniques for this region. The overall objective of this project is to combine and test innovative techniques such as solar light spectrum selective nanofluids, nano-enhanced phase change materials (PCM), and efficient solar-driven absorption cooling systems, which will result in sustainable, environmentally friendly and novel solutions for self-sufficient greenhouses/buildings capable of producing all type of needs, mainly; cooling, air conditioning, irrigation water, and electricity. Stand-alone solar energy-based applications are promising to resolve this issue. However, some challenges arise when solar energy is utilized for remote areas such as intermittency. The project team will solve this issue by deploying an effective nano-enhanced phase change material located underground through borehole heat exchangers that will provide necessary cooling and store heat/cold. In this project, solar energy is utilized as the energy source of an absorption cooling unit through innovative designs. Lithium bromide/water is the working fluid of the cooling unit, capable of lowering the temperature down to 4°C. The obtained cooling effect is utilized to dehumidify the ambient air for water condensation (to be used in the irrigation) and for dry air (to be used inside the greenhouse). This type of configuration enables a sustainable solution by having three required outputs in addition to electricity produced from concentrated photovoltaics (CPV). The project team will also employ an effective heat transfer method from CPV/T to the PCMs, which is nucleate boiling heat transfer. This method is particularly very suitable for absorption cooling units since they require heat source at about 80-120°C temperature levels. Hence, water can easily be used as the heat transfer medium in nucleate boiling. Furthermore, the project team will utilize a selective nanofluid as spectrum filtering mechanism to reduce the amount of non-useful photons entering the greenhouses. The sunlight is the natural source of energy and life for plants and animals in addition to humankind. Sunlight is an electromagnetic wave consisting of photons having different wavelengths and intensities (from 280 nm to 4000 nm having a peak in the visible light region). The major driving force for the overheating of greenhouses in these hot areas like Qatar is the excess solar radiation, which is not utilized by the plants. The photosynthesis occurs between wavelengths of 400 nm and 750 nm due to selectivity of chlorophyll pigment, which does not fully absorb even the complete visible spectrum due to its nature. Therefore, the energy converted by crop photosynthesis in a greenhouse is almost less than 1% of the available solar energy, which is very small amount considering the heat load of the greenhouse. About 50 to 60% of the absorbed solar radiation is converted to latent heat by crop evaporation and the remaining sensible heat increases greenhouse temperature. Presently, conventional cooling by ventilation is applied to withdraw the excess sensible heat from the greenhouses. Therefore, there arises a high cooling load in regions with dry outdoor conditions. The project team proposes to eliminate the problem at the source level by blocking the non-useful photons (above 750 nm) entering the greenhouses. In this way, significant portion of the solar radiation contributing the temperature rise inside the greenhouse is not present. To achieve this task, a smart approach is followed in the project by employing spectrum splitting mirrors and/or spectrum-selective nanofluid filters. In this way, the spectrum for chlorophyll active region is allowed into the greenhouse, whereas the remaining portion starting from near infrared radiation (above 750 nm) is prevented from the entry. By reflecting the remaining portion, photosynthesis is not affected, and the greenhouse heat load is significantly reduced. The approach in this project does not only reflect the non-useful spectrum but also utilizes it for solar-driven absorption cooling unit and phase change materials as storage. In this way, the available energy is not wasted, and the reflected portion of the spectrum is used for additional cooling for the greenhouse. In addition, due to low operating temperature of absorption cooling unit (around 5-10°C), the obtained cooling is initially utilized for humid air harvesting to condense water and use in the irrigation.

Submitting Institute Name

Hamad Bin Khalifa University (HBKU)
Sponsor's Award NumberNPRP12S-0123-190011
Proposal IDEX-QNRF-NPRPS-1
StatusActive
Effective start/end date1/04/2014/07/25

Collaborative partners

Primary Theme

  • Sustainability

Primary Subtheme

  • SU - Environmental Protection & Restoration

Secondary Theme

  • Sustainability

Secondary Subtheme

  • SU - Sustainable Energy

Keywords

  • Cooling,Heat transfer,Solar energy,Nano material,Optimization
  • Heat transfer
  • Solar energy; Nano material; Optimization

Fingerprint

Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.