Liquid and solid desiccant systems are vital in HVAC applications that require the effective removal of moisture while maintaining desired temperatures. This dual function significantly reduces the energy required to achieve the desired supply air conditions for either comfort or to maintain desired temperature and humidity conditions required for a variety of industrial applications. These desiccant-based approaches enhance heating and cooling efficiencies, which improve energy management (use) and indoor climate control and comfort.

This article will explore the cooling and heating requirements of liquid and solid desiccant systems in HVAC applications. We will compare their operation under different climatic conditions and provide practical insights in selecting the appropriate choice.

Comparative Analysis of Liquid and Solid Desiccant Systems

Here is a detailed comparison of how liquid and solid desiccant systems perform under various climatic conditions:

Operation

Liquid desiccant systems operate by directly cooling the circulating desiccant (or brine) solution, which allows such systems to effectively absorb moisture from the air that comes into contact with the liquid. This process simultaneously dehumidifies and cools their air, making the liquid system highly efficient in managing both humidity and temperature, particularly in humidity-dominant applications

Comparatively, solid desiccant systems require the outside air to be pre-cooled to a saturated state before moisture and contaminants are absorbed into the desiccant’s pores. As this process is exothermic, the supply air also frequently needs post-wheel cooling before distribution to the target areas to be cooled.

Efficiency

Liquid desiccant systems exhibit high dehumidification efficiency. However, their efficiency decreases in cooler and drier climates where less moisture needs to be removed. Conversely, solid desiccant systems are generally more efficient in cooler, dry climates with lower dehumidification needs. However, they may require supplementary cooling systems in extremely humid environments.

Energy Consumption

Liquid desiccant systems typically require less regeneration energy than solid desiccant systems. This efficiency makes liquid systems more suitable for hot and humid environments, since, at these conditions, they effectively remove moisture from the air while also consuming less energy. By comparison, solid desiccant systems require substantially higher temperatures for regeneration, which can be punative. In addition, the need for post-cooling of supply air before distribution into comfort zones, particularly in humid climates, also presents an inefficiency.

Environmental Impact

The environmental impact of such systems is directly related to energy efficiencies. Liquid desiccant systems can reduce the reliance on less-efficient traditional mechanical air conditioning, which results in lower energy usage and thus, lower greenhouse gas emissions from the power sources employed. These liquid systems can regenerate at low temperatures or can be integrated with renewable sources of energy, such as solar or waste heat, which further reduces the reliance on fossil fuel sources and thus reduces the environmental impact.

Moreover, solid desiccant systems, while effective at removing moisture in many applications, require significant energy due to the high temperatures required for regeneration and the need for pre-wheel and post-wheel cooling processes. They also use a bit more fan energy than liquid desiccant systems because of their larger pressure drops.

Technical Nuances

Liquid desiccant systems effectively maintain desired temperature and humidity levels, ensuring consistent cooling and dehumidification performance at a variety of target conditions. These systems excel in high-humidity applications and in humidity-dominant applications.

On the other hand, solid desiccant systems can offer reliable temperature and humidity control but may require additional systems to operate in very hot or very cold environments. They are effective at managing humidity levels; however, in areas with high humidity, they may need to be regenerated more frequently, which can be energy-intensive.

Key Factors for Selecting a Desiccant System

The following factors will help you choose the appropriate desiccant system based on your specific heating and cooling needs:

Installation Requirements

When choosing between desiccant systems, prioritize their integration with existing HVAC setups. While liquid desiccant systems may seem to be more complex, while solid desiccant systems may offer simpler setups, both are still suitable for straightforward applications. Additionally, ensure both systems are plug-ready, seamlessly integrating into existing AHU systems for efficient functionality.

Maintenance Demands

Maintenance requirements can differ significantly between liquid and solid desiccant systems. Liquid desiccant systems typically require periodic air and liquid filter changes, and routine monitoring of fluid concentration Solid desiccant systems also require comprehensive maintenance, including air filter changes, bearing greasing, seal checks, and ensuring positive pressure on the supply air side. Solid desiccant wheel fouling can result from poor air filtration.

Overall Lifecycle Costs

Liquid desiccant systems may require a higher initial investment than solid desiccant systems. Despite this, their lower energy usage and maintenance costs often result in an ROI of less than two years, and in some cases less than one year. Conversely, solid desiccant systems, though initially cheaper, may encounter higher maintenance costs due to their sensitivity to temperature fluctuations. They are more affected by changes in temperature, which can lead to reduced performance or even physical degradation of the desiccant material.

System Efficiency

Consider the system’s efficiency in your specific environment. Assess how well each desiccant system performs under your operating conditions, and for conditions of partial system loads. Additionally, any potential need for auxiliary systems to support independent temperature and humidity control should be taken into account. This will help ensure that the chosen system effectively and efficiently meets your heating and cooling needs.

Reduce Emissions With AirGreen’s Advanced Desiccant HVAC Technology!

At AirGreen, we help combat climate change by offering innovative HVAC and dehumidification solutions that are substantially more energy efficient, thus reducing source greenhouse gas emissions. Our advanced liquid desiccant systems provide superior comfort and efficiency and help our customers use far less energy. Choose us for a sustainable, energy-saving alternative to traditional mechanical conditioning systems!

Contact us now or request a quote today.