4 FM quick reads on HVAC
1. Geothermal Systems Offer Efficient Heating and Cooling
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is geothermal heat pump systems.
Geothermal systems have garnered new attention because of the growing interest in green design. Geothermal systems work by transferring heat to and from the ground or ground water. In cold weather, the liquid in the pipes draws heat from the subsurface; in warm weather, heat from the building is transferred into the ground.
In the most common design, closed loops of pipes are placed into the ground. In vertical systems, wells are dug 300 or more feet deep for the pipes. In horizontal systems, the pipes are laid in trenches 6 to 10 feet underground and are usually used for smaller buildings.
The environmental benefit is simple: Geothermal systems provide heating and cooling without the use of fossil fuels. What’s more, they use technology that is simple, reliable and efficient, with operating costs up to 60 percent less than conventional systems. But they are significantly more expensive to install. Paybacks range from 5 to 12 years. The systems may qualify for tax deductions under the federal Energy Policy Act of 2005. Geothermal systems are good candidates for those tax benefits.
Investments in Maintenance Will Extend HVAC System Life
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is the role of maintenance investments in extending the life of HVAC systems.
Facility executives are well aware of the impact that new HVAC equipment can have on the organization’s bottom line. From variable frequency drives to variable air volume systems, from chillers to boilers, investments in HVAC efficiency can produce significant energy savings.
But achieving those savings over the life of HVAC systems requires that the units be kept in good operating condition. And that takes money.
Whether it’s a pump or a control, performance falls off as equipment ages. Preventive maintenance is the way to stay ahead of the curve. Waiting until something goes wrong will often increase energy costs and decrease occupant comfort and reliability. In the worst case, a wait-and-see attitude can dramatically reduce equipment life.
It’s not only the operating budget that should include funds for effective maintenance. The initial design should be based on maintainability. For example, it’s important that there be sufficient space around equipment to enable staff to perform needed maintenance. That may cost a little extra, but saving money on maintenance is a classic case of being penny-wise but pound-foolish.
Low-Temperature Air Distribution Can Reduce Costs
Typical HVAC systems distribute air cooled to 55 degrees. If lower temperature air is used – for example, 48 degrees – both construction and operating costs can be reduced. The reason is that less air has to be moved if the temperature of that air is lower. That allows smaller ductwork and fans to be installed during construction. And operating costs are lower because less fan power is required to move the air and because the economizer mode can be used for more hours.
With low temperature air distribution, it’s important to ensure that the colder air does not reach occupants directly. It’s also essential to prevent condensation by using continuous external insulation with a vapor barrier even at spots where insulation isn’t typically used, such as the return bends of hot water reheat coils.
The use of a thermal storage system is one way to produce the colder chilled water required for low temperature air distribution
Thermal Storage Can Minimize Demand Charges
I’m Ed Sullivan, editor of Building Operating Management magazine. Today’s topic is using thermal storage to minimize demand charges.
Facility electric bills have two basic components. One is consumption – the amount of energy used. The other is a demand charge, which is based on a facility’s peak demand. The demand charge may reflect the highest peak demand in an entire year.
Thermal storage systems can help minimize demand charges. Thermal storage systems create ice or cool water at night, when rates are low, then use that ice or cool water to provide cooling during the day. That reduces consumption of power during the hours of peak demand, reducing the demand charge.
In addition to its impact on operating costs, a thermal storage system can also reduce the construction cost of the mechanical system. That’s because the HVAC system can be downsized based on how much of the peak load the thermal storage system can handle.
Life-cycle cost optimization can be used to help determine how much of the load the thermal storage system should be designed for.