Rethinking Outdoor Air: How Blue Frontier’s BF-DOAS Combines Dehumidification, Cooling, and Energy Storage

Commercial buildings need increasing amounts of outdoor air to support indoor air quality, occupant comfort, and changing ventilation requirements. However, bringing hot, humid air into a building creates a significant cooling and dehumidification load. Conventional HVAC systems typically address this load by cooling the air below its dew point and then reheating it to an acceptable supply temperature.

Blue Frontier takes a fundamentally different approach.

The Blue Frontier Dedicated Outdoor Air System, or BF-DOAS™, uses a liquid-desiccant-enhanced, two-stage conditioning process to control humidity and temperature independently. It also incorporates thermal energy storage, intelligent controls, and grid-responsive operating capabilities into a packaged outdoor-air system.

The result is not simply another high-efficiency DOAS. It is a load-shaping HVAC platform designed to improve indoor air quality, reduce peak electrical demand, and give facility operators greater control over when cooling energy is consumed.

What Is the Blue Frontier BF-DOAS?

The BF-DOAS is a packaged dedicated outdoor air system designed to condition high percentages of ventilation air. Rather than relying exclusively on a conventional direct-expansion vapor-compression cycle, the unit uses a proprietary, noncorrosive liquid desiccant to remove moisture from the incoming air.

The conditioned air then passes through a sensible cooling stage that reduces its dry-bulb temperature to a room-neutral supply condition. This two-stage architecture allows the system to manage latent and sensible loads independently.

Blue Frontier can deliver 100% outdoor air at a typical 55°F dew point and a room-neutral supply-air temperature without conventional overcooling and reheat. By removing moisture isothermally rather than cooling all incoming air to the dew point, the system avoids one of the major energy penalties associated with traditional DOAS operation.

How the Technology Works

The BF-DOAS conditioning process can be understood as two primary stages.

Stage 1: Liquid-Desiccant Dehumidification

Outdoor air first enters the conditioner core, where the liquid desiccant absorbs water vapor directly from the air. An indirect evaporative cooling process helps control the air temperature as moisture is removed.

Outdoor air enters at approximately 95°F dry bulb and 76°F wet bulb. The liquid desiccant removes moisture while an indirect evaporative cooler helps maintain the air’s dry-bulb temperature.

This is significant because conventional systems generally remove moisture by cooling air below its dew point. That process creates a mixture of sensible and latent cooling, often producing air that is colder than the space requires.

Stage 2: Sensible Cooling

After dehumidification, the dry air moves through a counterflow indirect evaporative cooler. This stage reduces the dry-bulb temperature to a room-neutral condition without adding moisture back into the supply air.

Because dehumidification and sensible cooling are handled separately, each can be modulated according to actual building conditions. This architecture enables more precise humidity control and reduces the need for energy-intensive reheat.

What Makes the BF-DOAS Unique?

1. Independent Humidity and Temperature Control

One of the BF-DOAS’s most important engineering distinctions is its ability to regulate humidity and temperature as separate variables.

In a conventional cooling coil, latent and sensible cooling are inherently linked. Lowering the coil temperature to remove more moisture also lowers the supply-air temperature. If the air becomes too cold, the system may need hot-gas, electric, or hydronic reheat.

Blue Frontier’s liquid-desiccant stage targets the latent load, while the sensible cooling stage establishes the final supply temperature. The system can therefore respond to changing outdoor-air conditions without forcing the sensible and latent capacities to track one another.

This can be particularly valuable during humid, part-load conditions when a building still requires substantial moisture removal but relatively little sensible cooling.

2. No Conventional Reheat Requirement

Many DOAS designs cool outdoor air to a low dew point and subsequently reheat it to prevent overcooling occupied spaces. Although effective, that sequence consumes energy twice.

The BF-DOAS removes moisture directly with its liquid desiccant and then cools the dry air to the required supply temperature. Blue Frontier identifies the elimination of conventional reheat as a core feature of the system.

For engineers, this can simplify the energy model by reducing or eliminating a potentially significant reheat load. Actual savings will depend on climate, ventilation requirements, supply-air setpoints, utility rates, and the baseline system used for comparison.

3. Integrated Thermal Energy Storage

The BF-DOAS includes energy storage within the unit rather than relying on a separate chilled-water tank or electrical battery.

Tthe system’s storage can provide approximately four to six hours of cooling at target setpoints. During discharge, the energy-intensive regeneration process can be turned off while the unit continues operating its fans, small pumps, sensors, and controls. The company reports an electrical draw of approximately 1,800 watts during this operating mode.

This gives facility operators the ability to shift a substantial portion of ventilation cooling away from expensive or grid-constrained periods.

Potential operating strategies include:

• Charging storage during off-peak utility periods

• Charging when on-site solar generation is abundant

• Discharging during utility peak-demand windows

• Participating in demand-response programs

• Reducing demand charges

• Aligning HVAC consumption with lower-carbon electricity

• Supporting virtual power plant or grid-interactive building programs

Unlike a conventional battery, the storage medium is used directly in the air-conditioning process. The unit is storing cooling and dehumidification capability rather than converting electricity into chemical storage and then back into electricity.

4. High Moisture-Removal Efficiency

Moisture Removal Efficiency, or MRE, is particularly important for dedicated outdoor air equipment because DOAS performance is frequently dominated by the latent load.

Blue Frontier has an ISMRE2 rating of 9.2 lb/kWh for the BF-DOAS. Its technical brochure compares this with a proposed ASHRAE minimum of 3.8 lb/kWh, although engineers should verify the applicable standard, rating procedure, and jurisdictional requirements for each project.

The system achieves approximately three times the moisture-removal efficiency of the referenced minimum. That performance makes the technology especially interesting in humid climates and buildings with high outdoor-air fractions.

5. Performance During Hot and Humid Conditions

Conventional air-conditioning equipment can experience declining capacity and efficiency as outdoor temperature rises. The latent and sensible capacity of the BF-DOAS can increase as ambient temperature and humidity increase because higher ambient temperatures support the desiccant regeneration process.

This characteristic could be valuable during design-day conditions, when the building, HVAC equipment, and electrical grid are under the greatest stress.

Engineers should still evaluate the system against location-specific design conditions, bin-hour weather data, entering-air psychrometrics, required leaving conditions, and project-specific redundancy requirements.

6. Reduced Dependence on Condenser Fans

Because the core dehumidification process does not follow a traditional vapor-compression-only architecture, the BF-DOAS does not use a conventional outdoor condenser arrangement in the same manner as a typical DX rooftop or DOAS unit.

Blue Frontier highlights the absence of conventional condenser-fan noise as a benefit. This can be useful where outdoor sound levels, nearby occupied spaces, property lines, or rooftop acoustics present design constraints.

7. Intelligent Controls and Digital-Twin Services

The system includes factory-mounted programmable logic controls, standard building-management-system communication capabilities, and a web-based interface for operating data.

Blue Frontier has digital-twin monitoring and predictive maintenance as lifecycle features. According to the company, remote monitoring is used to supervise system operation and liquid-desiccant concentration.

For an engineering or facility-management team, these capabilities may support:

• Fault detection and diagnostics

• Remote performance monitoring

• Predictive maintenance

• Energy-storage scheduling

• Demand-response dispatch

• Supply-air dew-point verification

• Trend analysis

• Measurement and verification

• Optimization based on utility tariffs

The practical value will depend on controls integration, available data points, BMS compatibility, cybersecurity requirements, and the responsibilities established between the factory, representative, contractor, and building operator.

Technical Specifications

Published information for the BF-DOAS includes the following specifications:

Parameter	Published Specification
Nominal capacity	15 tons
Available airflow range	2,000 to 3,500 CFM
Moisture removal rate	60 to 140 lb/h
ISMRE2	9.2 lb/kWh
Typical supply-air dew point	55°F
Dimensions	17 ft L × 6 ft W × 6 ft H
Unit weight	Approximately 6,500 lb
Embedded storage duration	Approximately 4 to 6 hours
Storage tank volume	150 gallons
Power during storage discharge	Approximately 1,800 W

The BF-DOAS is currently available in 15-ton and 20-ton capacities and can operate with a mixed-air inlet. Because product offerings can evolve, final capacity, airflow, electrical, structural, and control requirements should be verified with current submittal data.

Integration with Existing HVAC Systems

The BF-DOAS does not necessarily need to replace every piece of HVAC equipment serving a building. It can be applied as a ventilation-air system that works in parallel with existing packaged rooftop units or other zone-level equipment.

In a typical retrofit scenario, the BF-DOAS preconditions the required outdoor air and delivers it to the building or to existing air-handling equipment. Outdoor-air dampers at the existing rooftop units may then be reduced or closed, subject to the ventilation design.

Removing the outdoor-air latent load from the rooftop units can:

• Increase available return-air cooling capacity

• Improve part-load operation

• Reduce compressor runtime

• Improve indoor humidity control

• Reduce coil condensation risk

• Potentially extend the useful life of existing equipment

• Separate ventilation performance from zone sensible cooling

Blue Frontier specifically identifies preconditioning ventilation air for packaged rooftop units as an application, noting that relieving the rooftop equipment of the ventilation load can improve efficiency and increase return-air cooling capacity.

Example Applications Across Industries

Education

Schools and universities often have variable occupancy, high ventilation requirements, and limited opportunities for long mechanical shutdowns.

Potential applications include:

• Classrooms

• Lecture halls

• Student centers

• Administration buildings

• Gymnasiums

• Libraries

• Campus dining facilities

Separating ventilation dehumidification from zone cooling can help maintain more stable indoor humidity during mornings, evenings, summer breaks, and other low-sensible-load periods. Integrated storage may also allow a campus to shift cooling away from utility peaks or align operation with on-site solar generation.

Restaurants and Foodservice

Restaurants create a demanding combination of outdoor-air, exhaust, occupancy, and internal moisture loads. Makeup air introduced to offset kitchen exhaust can add a sizable latent load to the HVAC system.

A liquid-desiccant DOAS may be useful for:

• Full-service restaurants

• Quick-service restaurants

• Commercial kitchens

• Cafeterias

• Food courts

• Institutional dining facilities

Controlling the incoming-air dew point can reduce the burden on dining-area rooftop units and improve comfort during peak meal periods. Blue Frontier identifies a 24-hour restaurant as one of its field applications.

Healthcare and Senior Living

Healthcare environments frequently require controlled ventilation and careful humidity management.

Potential applications include:

• Outpatient facilities

• Medical office buildings

• Assisted-living communities

• Rehabilitation centers

• Common areas

• Administrative and support buildings

The ability to control latent and sensible conditions independently may help engineers maintain more consistent indoor conditions without excessive reheat. However, healthcare applications must be evaluated against applicable codes, filtration requirements, pressure relationships, redundancy criteria, infection-control standards, and owner-specific design guidelines.

Hotels and Hospitality

Hotels can experience high latent loads from outdoor air, showers, kitchens, laundry operations, entrances, and variable room occupancy.

Potential benefits include:

• Improved corridor and common-area humidity control

• Reduced latent load on guest-room systems

• Lower risk of condensation on diffusers and surfaces

• Better performance during low-occupancy periods

• Reduced peak demand during afternoon check-in periods

• Quieter exterior mechanical operation

In humid climates, a dedicated source of dry ventilation air can also help prevent guest-room units from becoming the building’s primary dehumidification mechanism.

Office Buildings

Office buildings often have predictable occupied schedules and utility demand peaks, making them logical candidates for load-shifting strategies.

The BF-DOAS could charge its storage before or after the utility’s peak window and discharge during high-cost afternoon periods. The system may also coordinate with rooftop photovoltaic generation, building automation schedules, and demand-response events.

Blue Frontier lists an office application integrated with renewable energy among its field examples.

Retail and Grocery

Retail facilities can have large ventilation loads, frequent door openings, fluctuating occupancy, and extensive packaged rooftop equipment.

Potential applications include:

• Shopping centers

• Big-box retail

• Supermarkets

• Pharmacies

• Convenience stores

• Fitness centers within retail developments

In grocery environments, better control of ventilation-air humidity may help reduce moisture migration toward refrigerated cases and conditioned sales floors. Any projected refrigeration savings should be modeled based on store layout, case type, infiltration, pressure relationships, and local climate.

Industrial and Manufacturing Facilities

Industrial buildings may require outdoor air for occupants, process exhaust makeup, pressurization, or contaminant control.

Potential applications include:

• Light manufacturing

• Electronics assembly

• Pharmaceutical support areas

• Warehouses with conditioned zones

• Laboratories

• Process-support spaces

• Facilities with significant exhaust requirements

Where low-grade waste heat is available, there may be additional opportunities to support desiccant regeneration. The system can operate using heat streams around 122°F from sources such as data centers, refrigeration loops, and industrial processes. Site-specific heat quality, availability, temperatures, flow rates, and heat-exchanger requirements would need detailed engineering evaluation.

Data Centers and Technology Facilities

Although data centers are primarily sensible-cooling applications, they often reject substantial amounts of heat. That heat may have value elsewhere in the facility.

A BF-DOAS could potentially provide ventilation and humidity control for occupied or support areas while using an available heat stream for regeneration. This creates a potential heat-recovery relationship between the data-center cooling infrastructure and building ventilation equipment.

The engineering analysis should consider seasonal heat availability, water temperatures, redundancy, controls sequencing, heat-exchanger approach temperatures, and the relative location of the systems.

Public and Municipal Facilities

Government and public buildings frequently operate under energy-reduction, resilience, and sustainability mandates.

Potential applications include:

• Administrative facilities

• Libraries

• Community centers

• Public-safety buildings

• Transit facilities

• Recreation centers

• Emergency operations support areas

Embedded storage may allow these facilities to reduce cooling demand during grid emergencies without sacrificing ventilation or indoor comfort.

Grid Resilience and Demand Management

Air conditioning is a major contributor to summer electrical demand, especially during late-afternoon heat events. Blue Frontier positions the BF-DOAS as a grid-edge resource because the system can separate the time when it consumes significant energy from the time when the building needs cooling.

The systems can shift approximately four to twelve hours of cooling, depending on configuration and operating conditions, without the use of an electrical battery. Its current packaged-unit literature more commonly identifies four to six hours of embedded storage at rated operating conditions.

This flexibility can support:

• Peak-demand reduction

• Time-of-use rate optimization

• Renewable-energy utilization

• Demand-response participation

• Utility capacity planning

• Building electrification strategies

• Virtual power plant programs

• Reduced stress during extreme heat

For utilities, this represents a behind-the-meter resource that can potentially be deployed faster than large generation, transmission, or distribution projects.

For building owners, the more immediate value may come from lower demand charges, reduced operating costs, improved humidity control, and possible participation incentives.

Engineering Considerations

Before specifying the BF-DOAS, the design team should evaluate several project-specific factors.

Psychrometric Requirements

Engineers should define:

• Outdoor design dry-bulb and wet-bulb conditions

• Required supply-air dew point

• Required room-neutral supply temperature

• Ventilation airflow

• Space latent loads

• Exhaust and makeup-air relationships

• Building pressure requirements

• Seasonal part-load conditions

Annual bin-hour modeling may reveal more value than a design-day-only comparison because much of a DOAS’s energy use occurs in humid, part-load conditions.

Structural and Spatial Requirements

A published unit weight of approximately 6,500 pounds and a footprint of roughly 17 by 6 feet require early coordination with structural, architectural, and site disciplines.

Design teams should evaluate:

• Roof loading

• Equipment curbs or structural steel

• Ground-mounted alternatives

• Crane access

• Service clearances

• Replacement access

• Roof penetrations

• Vibration isolation

• Wind and seismic requirements

Controls Integration

The sequence of operation should define:

• Supply-air dew-point control

• Supply-air temperature control

• Storage charging and discharging

• Utility peak avoidance

• Demand-response commands

• Occupancy scheduling

• Outdoor-air reset

• Alarm priorities

• Fallback operating modes

• Communication with rooftop or zone systems

Storage dispatch should be coordinated with utility tariffs, weather forecasts, occupancy, and anticipated cooling demand.

Maintenance

The desiccant can absorb and release water through repeated cycles without routine replacement. Filtration changes for the desiccant and water circuits should be performed at approximately six-month intervals as the major routine maintenance activity.

A project’s maintenance plan should still address:

• Air filters

• Liquid-circuit filters

• Pumps

• Sensors

• Dampers and actuators

• Fans and motors

• Water quality

• Heat exchangers

• Controls calibration

• Remote-monitoring responsibilities

A Different Way to Think About Air Conditioning

The Blue Frontier BF-DOAS addresses three challenges that are usually handled separately: ventilation, humidity control, and grid-responsive energy management.

Its liquid-desiccant architecture separates moisture removal from sensible cooling. Its embedded storage shifts energy consumption without relying on a conventional electrical battery. Its controls platform gives operators the ability to respond to building needs, utility signals, and changing outdoor conditions.

For engineers, the technology is especially compelling where a project has:

• High ventilation requirements

• Significant latent loads

• Expensive peak electricity

• Demand charges

• On-site renewable generation

• Strict humidity requirements

• Existing rooftop units burdened by outdoor air

• Available low-grade waste heat

• Grid-resilience or decarbonization objectives

The BF-DOAS may not be the optimal solution for every building. However, for facilities where outdoor air, humidity, and peak demand are persistent design challenges, it offers a genuinely different engineering path.

Rather than treating air conditioning as an inflexible load that becomes more problematic during hot weather, Blue Frontier turns ventilation cooling into a controllable building resource. That combination of indoor-air performance, operational efficiency, and energy flexibility may make the BF-DOAS an important part of the next generation of commercial HVAC design.