Get answers to frequently asked questions about thermal energy storage.
In many cases storage systems are no more expensive than conventional systems. And we’ll almost always be able to work within a very realistic 3 to 5 year payback.
Absolutely – storage systems can incorporate equal, or greater, redundancy than conventional systems. It all depends on the demands of the application. Sometimes multiple chillers provide enough redundancy and other times backup chillers (N+1)are needed – just like conventional systems. And if utility power is lost, storage can continue to provide cooling with only modest backup power requirements.
One of the benefits of ice storage is the very high energy density provided by the phase change of ice to liquid water. About ¼ of 1% of the building floor area is needed for a typical partial storage application that meets 30-40% of the building peak cooling load. Full storage systems will require a little more than double that area. But remember, the CALMAC modular storage approach allows you to tuck tanks into a lot of different areas. We have buried and partially buried tanks, tanks on roofs, in basements, outdoors, on mezzanines and just about any where else you can think of.
Demand charges still provide the incentive for most of our installations, but these demand charges are increasingly being obscured within complex rate structures – but be assured, you are paying for peak demand one way or another. Some rates are based on ‘use of demand’ where the kWh charge is tied to the number of kWh’s at different demand levels. Sometimes the demand charge is a function of your specific demand at the time the utilities are providing their peak capacity (coincident peaks). Third party providers often quote flat rates, but they have incorporated your demand profile into the estimate – and you can benefit from offering them a more stable load profile.
It depends. A building with thermal storage presents a very attractive demand profile to the utility. Energy providers who want your business will negotiate to incorporate your added value into that flat rate – but you have to be willing to invest effort into making sure your value is rewarded.
This is an often confusing issue for potential thermal storage customers. There are a lot of variables that impact the comparative efficiency of storage and conventional systems. In many, if not most cases, the system design and day/night weather patterns will result in a kWh savings at the building. In some cases, the building may consume slightly more kWh. However, when we look at the overall efficiency of the generation, distribution and consumption of electrical power, thermal storage almost always provides a distinct advantage. Power plants operate more efficiently at night and transmission losses are at their lowest. The dirtiest of the peaking plants are not operating. You’ll be burning less fuel and you’ll be saving money.
Certainly, but the size of the nighttime cooling load, relative to the daytime peak, may change how we design and control the system. But, yes, it is quite common.
All of the components, other than the storage tanks, are completely familiar. The system operates with a secondary coolant, like glycol, rather than plain water. In some cases, we may suggest the use of a heat exchanger to separate the storage loop from the building distribution network. Even though the components will be familiar, the arrangement may be different from what you are used to seeing – storage provides a lot of flexibility. Often the most important consideration is controls. This is where CALMAC’s, and our representative’s experience really provides valuable support. We know storage systems, we understand utility rates, we appreciate the importance of simplicity and we are committed to making sure every system operates as intended.
If your prospective tenants can save on utility costs, it makes your building a more attractive property. If your building can provide more value to your tenants, it will provide more value to you also. And it happens to be a good thing to do for all of us.
Amidst all of that turmoil there is one stable and unwavering economic reality – off-peak electricity is the only energy source that has not increased in cost over the last 40 years. Why wait any longer to take advantage of low cost off-peak power?
There is no doubt that unitary systems can be more difficult to incorporate storage. CALMAC has successfully converted unitary systems to chiller based storage systems, continuing to utilize the existing distribution structure to manage costs. If interested, we’d be happy to discuss the possibilites – and we’ll be realistic in evaluating whether thermal storage is your best option.
Rebates are usually put out by utilities to get an ice storage market moving or to help a market that might have more costs involved, such as an urban area. Most areas of the country do not have rebates and storage is very applicable because savings can be realized by shifting electricity consumption and purchase to low cost night time electricity. The Edison Electric Institute (EEI) has said that night time or off peak electricity is the only form of energy that has not increased in price, in today’s dollars, in the last 40 years.
Yes, with proper preparation the tanks can be re-deployed for use in other locations.
Utilities change their rates and rebate programs constantly so keeping up with them is a challenge, however this website http://www.dsireusa.org/ does a good job at keeping track of efficiency rebate programs. Alternatively, keeping track of electricity rates is what we do every day so please contact your CALMAC representative for up to date information on your local rates.
The electricity rates favor shifting consumption off peak. Additionally years of product and control advancements have made the technology more reliable while over 25 years of best design and operation practices have made the system more efficient and dependable.
Yes, the internal melt ice on coil technology uses a secondary heat transfer fluid. The fluids typically used are ethylene (25% min. concentration) or propylene glycol (29% min. concentration). Other fluids can be used as well. Check with chiller manufacturer and CALMAC before consideration. Glycol may be seperated from a building with use of a CALMAC plate heat exchanger.
No, the water in the ice storage tanks is static and does not leave the tanks.
No, most absorption chillers use water as a refrigerant which makes ice making impossible.
Maintenance requirements are quite simple. Every year check the water level of the tanks and fill to the proper level is necessary. Check and treat, if necessary, the concentration and health of the heat transfer fluid annually, and recalibrate the controls and modes of operation to make sure that the operation of the ice tanks are corresponding properly and are operating correctly for the current electricity rate.
The ice tank is designed and manufactured to provide a reliable and long useful life. With proper maintenance the IceBank can have a useful service life of 30 years and is 99% reusable or recyclable. There are no moving parts and the major components are made of polyethylene. Polyethylene pipe is used throughout the world for long term reliable distribution of natural gas which lists a useful life of fifty years.
The number of ice making hours varies by project and depends upon the facility usage. Usually the ice tanks are recharged between eight and 10 hours. Some projects might have a shorter recharge time. Some might be longer.
It depends on the load profile and your utility rate. The greater the difference between on peak and off-peak cooling demand, the greater the potential benefit of thermal storage. Hotels and hospitals have areas with near constant cooling demand, but very often also have significant loads that fluctuate dramatically and provide opportunity for storage. Schools have always been excellent candidates for thermal storage. With the growing application of air-conditioning to classrooms as well as the gradual extension of the school year, the interest in thermal storage by school boards is intense. Residential applications for cooling storage are more difficult to justify because there is rarely a utility rate that rewards off-peak energy use – at least without severe penalties for on-peak consumption. However, the residential air-conditioning peak is having a real impact on utilities and this may change. Take this quick survey to see if thermal storage makes sense for your building.
Of course there are ‘best practices’ to follow in designing a thermal storage system, but if you are familiar with central, chilled water system design, you already have most of the required knowledge. And CALMAC has over two hundred years of combined TES engineering and application knowledge – and the enthusiasm to share that knowledge with all our customers.
It varies by type, but Calmac’s products were designed to be simple from the start. They are made to incorporate into standard chilled water systems, have no moving parts and are completely corrosion proof. All the other equipment is identical to what you normally find in a chilled water system.
CALMAC’s ice storage products are designed to integrate easily into conventional chilled water systems. There is some added complexity for control sequences, but major manufacturers have developed ‘canned’ control routines and many chiller lines even have ice building logic built into their standard programming. And CALMAC has over thirty years of storage controls experience in virtually every type of application.
TES is often installed to reduce risk. Stored cooling can provide cooling capacity when chillers are disabled or their operation interrupted. Any level of redundancy can be incorporated into storage designs - just like conventional systems.