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Cool Thermal Energy Efficiencies

Delphi Thermal Systems has developed heating and cooling solutions that improve vehicle energy efficiency while lessening the impact on the environment. 

Soaring gasoline prices. Global warming. Dwindling fossil fuel reserves. No matter what the reason is for requiring more energy-efficient vehicles, Delphi is leading the way in developing innovative technologies for the vehicle manufacturer and consumer. As part of Delphi Corporation's commitment to provide vehicle components and systems with increasing energy efficiency, Delphi Thermal Systems contributes to a vehicle's increased fuel mileage and environmental friendliness in four major areas: HVAC (heating, ventilating, and air conditioning) systems, powertrain cooling systems, thermal systems for hybrid vehicles, and alternative refrigerants.

For example, a vehicle equipped with Delphi's air conditioning technologies alone can save a driver an average 5-15 gallons (19 - 57 liters) of fuel per year in the United States when compared to traditional air conditioning systems. At present fuel prices, that translates to $40 on an average of gasoline savings per vehicle every year of ownership and $500 over a 12-year vehicle life. Assuming 10 gallons (38 liters) are saved by every vehicle, it can quickly add up to an annual savings of 2.3 billion gallons (8.7 billion liters) or approximately $10 billion worth of gasoline per year in the U.S. Although the numbers stated here are for the U.S., Delphi's technology can result in fuel savings anywhere air conditioning is used.

"In addition to the energy-efficient systems and components developed by Delphi Thermal Systems, other divisions of Delphi are also doing their part to increase a vehicle's efficiency," said Marshall Andrews, automotive products business unit director, Delphi Thermal Systems. "Delphi Thermal works together with other Delphi divisions, to create a more efficient vehicle overall. To achieve higher efficiency, our teams consider reduced power consumption, reduced mass/weight/materials, and reduced emissions."

Recent highlights of this collaboration include new energy-efficient and green technologies in the areas of HVAC systems, powertrain cooling systems, thermal systems for hybrid vehicles, and alternate refrigerants.

1. HVAC Systems

Traditional air conditioning systems account for approximately 5 percent of a vehicle's fuel usage, or approximately 31 gallons (117 liters) per vehicle each year. Delphi's energy-efficient air conditioning technologies can help cut that amount in half.

"The key to an energy-efficient air conditioning system is to start with high efficiency components," said Mark J. Zima, engineering manager, Advanced HVAC Systems, Delphi Thermal Systems. "And as new technology becomes available, many times we can enhance system performance and energy savings with our patented algorithms."

Delphi technologies that help enable an energy-efficient HVAC system include Series Reheat Reduction, Air Inlet Mixture Control, and much more.

Series Reheat Reduction (SRHR)—When the outside air temperature is moderate, traditional cooling systems over-cool, dehumidify, and then reheat the ambient air, wasting fuel. Delphi's Series Reheat Reduction feature reduces compressor capacity to more closely match the reduced cooling demand, and also has the side benefit of improved humidity comfort for passengers.

"Delphi engineers have enabled this feature by creating proprietary software," said Zima. "Many vehicles require little or no new hardware for this added energy-saving feature."

Air Inlet Mixture (AIM) Control—When the outside air is hot, this feature reduces required compressor power while maintaining comfort. Cool, dehumidified compartment air is reused and combined with a lesser quantity of outside air. Compared with SRHR, AIM provides energy savings while maintaining comfort and providing plenty of fresh air to the vehicle occupants.

Stop/Start Thermal Storage—Energy savings are also being achieved through Start/Stop Thermal Storage technology whereby the engine is shut off when the vehicle stops either at a stop light or stop sign or when the vehicle is stationary in traffic. The actual energy saving can be limited by having to turn the engine back on during a stop to maintain passenger comfort. To enable the maximum savings for Start/Stop Thermal Storage equipped vehicles, Delphi has developed multiple technologies to store "cold" to use in cooling the cabin air when the engine is off. These include coolant and phase change material based systems.

Internal Heat Exchanger—This counter-flow, tube-in-tube pipe transfers the refrigerant from the evaporator outlet back over the pipe carrying the refrigerant headed to the evaporator. The refrigerant is then returned to the compressor. The compressor's efficiency is increased due to a consistent supply of superheated refrigerant and by maintaining the evaporator close to saturation.

Electronically Controlled Variable Displacement Compressor—Of the various existing compressor types, this compressor is considered the most energy-efficient. It separates oil internally to keep more in the compressor for better lubrication. Most importantly for energy efficiency, it adjusts its displacement or capacity to what is needed to keep the passenger compartment occupants comfortable. It can be precisely calibrated to achieve outstanding energy efficiency. There is also the potential for the next generation compressor to further separate and retain this oil. Minimizing the amount of oil circulating throughout the system will increase the heat exchanger's effectiveness and increase the compressor's isentropic efficiency.

Cycling Pneumatic Variable Displacement Compressor—One of Delphi's newest patent pending designs combines the benefits of Series Reheat Reduction with the inherent advantages of a pneumatically-controlled variable displacement compressor to generate one of the most cost effective and least complicated solutions for energy efficiency. Calibration is simple to achieve SRHR and the seamless stroke control by the pneumatic valve provides just the right amount of capacity for comfort. The cycling pneumatic variable displacement compressor is truly the best of both the fixed and pneumatically-controlled variable compressors.

Pulse Wide Modulated Blower Speed Controllers—Utilizing a new generation of microcontrollers, Delphi has developed an ultra-high efficiency variable blower controller to reduce waste energy by up to 95% and reduce mass by 40%, all at a competitive cost. The typical blower controller wastes excess electrical energy in a resistor or power transistor to create medium and low fan speeds. By using high efficiency switching technology, a typical energy savings of 45W results, reducing the electrical load on the alternator and improving fuel economy in real world applications. This energy saving technology is available for both HVAC blowers and powertrain cooling fans.

2. Powertrain Cooling Systems

Condenser Radiator Fan Module

The Powertrain Cooling (PTC) Module is backed by Delphi's 25 years of experience designing, integrating, and managing its assembly and logistics. The traditional module cools the air conditioning refrigerant, engine coolant, engine oil, and automatic transmission fluid. Module components include the condenser, radiator, oil coolers, fan-motor-shroud assembly and charge air cooler.

The module was designed with a combination of Delphi's overall system expertise in balancing the heat exchanger content with motor power and the various fluid flows. This capability is now more important than ever because new hybrid and turbocharged powertrains will have new requirements, requiring collaborative efforts between the electronics and powertrain areas of Delphi. Hybrid powertrains will require that the PTC Module cool electronics, batteries and traction motors. Turbocharged powertrains will require new levels of cooling for the charge air, now mixed with the exhaust gas. Delphi's next generation of charge air coolers positions the company well for this challenge.

Charge Air Cooler (CAC)—To achieve improved fuel efficiency as mandated by new fuel economy legislation, vehicle manufacturers are turning to new turbocharged engines. These engines are downsized and have more efficient combustion for enhanced engine performance and reduced emissions.

"Delphi is ready for this trend of CACs that cool the compressed air going to the engine," said Richard Rose, systems engineering manager, Advanced Powertrain Cooling, Delphi Thermal Systems. "And we are preparing for the next generation CAC that will be integrated with the air intake and exhaust systems."

3. Thermal Systems for Hybrid Vehicles

In addition to making conventional engine-driven vehicles more efficient, Delphi is researching and developing thermal systems and components for hybrid vehicles and fuel cells.

Many hybrid vehicles are being developed today—all with specific thermal needs compared to conventional powertrain vehicles. One of the unique characteristics of a hybrid vehicle is that its engine can shut-off at any time during a drive cycle— such as while waiting at a stop sign or stop light. Conventional vehicles use an air conditioning compressor that is belt-driven by the engine. When the engine shuts off, so does the air conditioning system. Delphi is developing two thermal technologies to enhance hybrid vehicle comfort when the engine is off.

Electric Compressor Air Conditioning System—For hybrid vehicles with sufficient electric energy storage on board, Delphi is developing an electric compressor-driven air conditioning system. This highly efficient and integrated system enables sustained air conditioning operation regardless of whether the engine is on or off. The system can be controlled to provide cabin comfort at various power levels to facilitate operating modes ranging from a high fuel economy mode to a high cooling comfort mode. This approach offers a wide range of options for consumers and is an enabling technology for extended "engine off" idle stops for commercial vehicle markets.

The heart of this system is Delphi's electrically driven compressor. This device integrates three main components: a high efficiency scroll pump, a variable speed electric motor, and an electric motor drive that, because it is integrated into the compressor body, is cooled with cold refrigerant returning to the compressor from the system. Delphi is planning to have a family of electric compressor designs to cover a wide range of vehicle applications from heavy duty trucks to small "plug-in" hybrid vehicles. The company's simple and efficient designs are being developed using lean manufacturing principles which will give Delphi the ability to deliver compressor designs best suited for each customer's specific application.

Hybrid vehicles with these electric compressor air conditioning systems will help set the comfort expectations for all hybrid vehicles. However, not all hybrid vehicles are designed with enough battery storage to enable electric compressor technology. For hybrid vehicles that do not have enough battery storage for electric compressors, Delphi is developing a "thermal storage" concept based on its secondary loop technology.

Secondary Loop Thermal Storage Air Conditioning System

Secondary Loop Thermal Storage Air Conditioning System—Delphi's secondary loop technology uses a conventional engine-driven compressor to drive the refrigeration system, just like conventional vehicles. However, instead of transferring heat directly from the HVAC air to the refrigerant, the heat is transferred through a "secondary loop" coolant to the refrigerant via a new Delphi heat exchanger called a "chiller." This secondary loop coolant is pumped to the HVAC module's "cooler," another new Delphi heat exchanger, to cool the HVAC air entering the vehicle. This "cold" coolant is stored on board a vehicle and used for "short durations" to maintain comfort when the engine and compressor are off.

Another significant benefit of a secondary loop air conditioning system is that it requires a smaller, more compact refrigeration system that is located completely under the hood. This smaller refrigerant system requires less refrigerant than a conventional direct expansion system, thereby lowering its potential impact on global warming.

Thermal storage air conditioning systems will enhance thermal comfort of those hybrid vehicle applications that are not designed for electric compressor air conditioning systems.

Hybrid Vehicle Battery Management and Power Electronics—There are many devices being developed specifically for hybrid vehicles that require thermal management.

Delphi Thermal Systems is working closely with Delphi Electronics & Safety to design and develop hybrid vehicle battery packs for a variety of applications. These battery packs are designed to maintain battery temperatures throughout the pack within strict temperature limits. Delphi Thermal is also collaborating with Delphi Electronics & Safety to engineer improved cooling methods for the next generation of hybrid vehicle power electronics. These electronic devices are becoming more power dense and are being packaged into smaller spaces, both of which contribute to the thermal management challenge.

Delphi Thermal Systems is also working closely with Delphi Powertrain Systems to design and develop heat exchangers and other high temperature devices that support the Delphi Powertrain Solid Oxide Fuel Cell (SOFC) project. "Because it operates at such high temperatures, the SOFC system requires special manifolds and heat exchangers," said John O'Brien, engineering manager, Advanced Propulsion & Fuel Cell Thermal Systems, Delphi Thermal Systems. "Our Thermal team works closely with Delphi Powertrain to develop high temperature product and process technologies that meet the strict demands of Delphi's SOFC system."

"Delphi engineers are looking ahead, imagining how vehicles will be powered and what they might look like 10-20 years from now," said O'Brien. "The vehicle market is changing rapidly and in order to stay ahead and be ready for the next generation of vehicles, we must be planning and developing new technologies now."

4. Alternative Refrigerants

The European Union has banned the use of the current refrigerant, R134a, for all new vehicle type approvals starting in the 2011 calendar year to reduce the greenhouse gas impact of direct refrigerant emissions (leakage). Three alternatives are under consideration: R1234yf, R744 and R152a. Throughout the selection process for viable alternative refrigerants, Delphi has remained in position to support vehicle manufacturers' decisions.

"Currently, R1234yf appears to be the refrigerant of choice by many original equipment manufacturers," said Tim Craig, engineering manager, Delphi Thermal Systems. "Its advantage is that the refrigeration properties are similar to R134a. It's very mildly flammable allowing use in a direct expansion system just as R134a is today. As a result, minimal HVAC modifications and no additional parts are required to achieve excellent performance levels."

In addition to applying the expertise gained by leading, Delphi has conducted in-house evaluations of refrigerant emissions or leakage in its state-of-the-art emissions lab. Delphi is also voluntarily working with the U.S. Environmental Protection Agency (EPA) to help reduce emissions and improve energy efficiency with Delphi HVAC components.

"Delphi is one of the world leaders in providing technology to reduce refrigerant emissions," said Craig. "We helped create and write the Society of Automotive Engineers emissions calculation (SAE J2727) methodologies and procedures. Delphi's compressors and fittings are given high marks based on J2727 standards."

Planning for the Future

Tomorrow's many cooling innovations from Delphi are in the works today. From concept to production, Delphi has energy efficiency, value, performance, durability, assembly ease, passenger comfort, and the best interests of both the original equipment manufacturers and vehicle owners in mind.

"Delphi Thermal is actively leading the industry in many areas of energy-efficient and climate friendly technologies," said Marshall Andrews. "We are bringing nearly 100 years of experience in this market to our customers with products that will help them design and sell vehicles that have the technologies that are in demand world-wide—and at a value that allows them to be competitive with their vehicles."

From fuel-efficient single components to integrated systems and next-generation enhancements to new products, Delphi Thermal Systems continues to provide thermal solutions with customers' needs in mind.

For more information about product offerings from Delphi Thermal Systems, click here.