RP1015: Combining a building integrated PVT system with a low temperature desiccant cooler to drive affordable solar cooling

_{Peer Reviewed Research Publications}

RP1015: Journal Article: Application of internal cooled desiccant wheel in air-conditioning system

Desiccant wheel based air-conditioning systems (DWAC) include a desiccant wheel component that performs latent cooling coupled to another component, for example an indirect evaporative cooler (IEC also known as a dew point evaporative cooler), that performs the sensible cooling without adding moisture into the air flow. Moisture removal in the desiccant wheel is approximately adiabatic due to heat carryover from the hot regeneration air stream and release of adsorption heat. This heating of the air being dried is unwanted and cannot only decrease both the sensible and latent cooling performance of the system but also requires a high temperature of regeneration air to drive the desiccant wheel to work in hot and humid climate. Ideally the moisture removal process for desiccant wheel would be isothermal instead of adiabatic. Thus, here we propose an internally cooled desiccant wheel design that offers nearly isothermal dehumidification and then use a mathematical model to analyze the performance of a complete DWAC system incorporating this component.

The new design uses 78.8°F (26°C) cooling water in the process section of the desiccant wheel as a cooling source to reduce the effects of adsorption heat and carryover heat. A model validated by the experimental data for internally cooled desiccant wheel and a commercial indirect evaporative cooler are then adopted to assess the performance of the DWAC system. Results show that for inlet air conditions of 95oF (35°C) and 60% relative humidity, the proposed DWAC system with internally cooled desiccant wheel could adsorb at least 0.0053lb (2.4g) moisture more (for per 2.2lb (1kg) dry air dry air) per second compared to a DWAC system using an adiabatic wheel when regeneration air temperature is 140°F (60°C) which could be easily gotten from a solar thermal collector. In addition, the electrical coefficient of performance for the internally cooled desiccant wheel system is calculated to be between 7 and 13 compared to 5.2 to 8.2 for the adiabatic wheel system. These results indicate that a DWAC system with an internally cooled wheel would be up to twice as efficient as the most efficient split system air-conditioners and three times as efficient as the Australian market average of new installed split systems in 2014 in hot and humid climate (dry bulb temperature is 95°F (35°C) and relative humidity is 60%).

Order the paper here: https://technologyportal.ashrae.org/papers/paperdetail/10439

RP1015: Journal Article: A review of photovoltaic thermal (PV/T) heat utilisation with low temperature desiccant cooling and dehumidification

One of the major obstacles to improving solar thermal cooling technologies is the high operating temperature requirements of most solar thermal cooling systems. This paper reviews recent advances that could reduce the required heat source temperatures for solar desiccant cooling to the range of 50°C–60°C. These approaches include (i) isothermal dehumidification (e.g. two-stage dehumidification or internal cooled dehumidification) and (ii) pre-cooling of the entry air with ambient heat sinks (e.g. indirect evaporative cooling or geothermal exchange). These techniques can potentially leads to a more thermodynamically efficient solution for utilising recovered heat from flat plate photovoltaic thermal (PV/T) collectors for desiccant regeneration.

Analysis of the literature shows that obtainable outlet fluid temperatures from existing PV/T systems nearly match the low temperature desiccant cooling and dehumidification applications. Design and operation factors for achieving sufficiently high outlet fluid temperature in flat plate PV/T collectors include (i) maintaining low mass flow rate per collector area, (ii) addition of a glazed cover and (iii) hydraulic channel diameter optimisation. These factors are reviewed and case studies of complete solar PV/T desiccant cooling are examined.

Read the full article here: http://dx.doi.org/10.1016/j.rser.2016.08.056 

RP1015: Conference Paper: Ground Coupled Photovoltaic Thermal (PV/T) Driven Desiccant Air Cooling

ground coupled photovoltaic thermal pv t driven dexiccant air cooling (432995 PDF)

RP1015: Journal Article: Performance investigation of an internally cooled desiccant wheel

Performance investigation of an internally cooled desiccant wheel - Applied Energy - Elsevier. Read HERE.