Centrifugal Chiller Compressors with Magnetic Bearings and Variable Speed Control

Summary

PDF

Centrifugal Chiller Compressors with Magnetic Bearings and Variable Speed Control

Chillers: Centrifugal Compressors with Magnetic Bearings and Variable Speed Control vs. Standard Rotary Screw Chiller

Refrigerant compressors that use magnetic bearings in lieu of lubricated mechanical bearings. They feature an oil-free design, with an integral super-premium efficiency permanent magnet motor for speed control and soft starting capability.

Synopsis:

Variable speed centrifugal chillers equipped with magnetic bearings save energy compared to conventional chillers by eliminating losses due to bearing friction. Part-load efficiency is improved through use of a variable speed drive and a compact design is achieved through operating at the ultra-high rotational speeds made possible through incorporating a super-premium efficiency permanent magnet motor into the design. Magnetic bearings also eliminate the maintenance costs associated with conventional metal bearings. Available compressors are also oil-free which further reduces maintenance requirements with the variable speed drive also allowing for soft start capability (soft-starting with a reduced amperage draw imposes a lighter load on backup generators, which may be of importance in some industrial sites) (From: FEMP Promising Technologies List).

Energy Savings: 30%

Energy Savings Rating: Limited Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 7.2 What's this?

Simple Payback, Retrofit (years): 7.2 What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

Details

PDF

Centrifugal Chiller Compressors with Magnetic Bearings and Variable Speed Control

Chillers: Centrifugal Compressors with Magnetic Bearings and Variable Speed Control vs. Standard Rotary Screw Chiller

Item ID: 109

Sector: Commercial

Energy System: Refrigeration--Refrigeration Systems

Technical Advisory Group: 2009 HVAC TAG (#2)

Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
Average TAG Rating: 2.95 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:

There are only marginal increases in chiller efficiency. This is not where the big savings are.
There is very little potential for this technology in BPA's territory.
Widely available in a tremendous range of sizes from multiple OEMs. The program Q that I once worked on was how to build a chiller replacement program that would focus on the remaining stock of obsolete, low-efficiency, CFC-refrigerant chillers: modern units get rid of the ozone depletion, much of the GWP, and are almost twice as efficient.
I'd like to see these in more HVAC applications, and I think the technology could be transferred to refrigeration compressor systems, with some research or potential cascade systems.
I think it requires more testing
Much improved efficiency for these type of chillers - heat pump systems eliminate the need for water cooling and water use.

Synopsis:

Baseline Example:

Baseline Description:
Baseline Energy Use: 7.4 kWh per year per square foot

Comments:

The 2009 Commercial Building Stock Assessment gives the actual electrical building energy use index (EUI) for various types of heating and cooling systems (Table D-EA5). Office buildings with electric heating and cooling have an EUI of 20.1 kWh/sf/year. Office buildings with no electric heating or cooling use only 8.2 kWh/sf/year, indicating that the combined HVAC heating and cooling energy use is 11.9 kWh/sf/year. For all commercial buildings, the corresponding numbers are 19.9 and 9.4 kWh/sf/year,respectively for a heating and cooling use of 10.5 kWh/sf-year.

Commercial buildings with electric cooling and with no electric heating have an electrical EUI of 16.8 kWh/sf-year (14.8 for office buildings). This indicates that the heating load for all categories of commercial buildings is about 3.1 kWh/sf-year (19.9-16.8) with a cooling load of about 7.4 kWh/sf-year (10.5-3.1). The corresponding electrical EUI for office buildings with electric cooling with no electrical heating is 14.8 kWh/sf-year which indicates a space heating load of 5.3 kWh/sf-year with a corresponding cooling load of 6.6 kWh/sf-year (11.9-5.3).

Since this technology can be applied to many types of buildings, a baseline commercial building and cooling energy use of 7.4 kWh/sf/year is assumed (NEEA, 12/21/2009).

Manufacturer's Energy Savings Claims:

Savings Range: From 10% to 50%

Comments:

Best Estimate of Energy Savings:

"Typical" Savings: 30%
Low and High Energy Savings: 10% to 42%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

Testing of a 150-ton chiller screw compressor showed a full-load performance of 0.715 kW/ton. An equivalently sized Turbocor compressor performed at 0.645 kW/ton for a 9.8% improvement. When the Integrated Part-Load Value (IPLV) performance was measured, the conventional screw chiller performance was measured at 0.546 kW/ton while the Turbocore performance was improved to 0.371 kW/ton---for an energy savings of 32% in this example (WSU EEP, 2006). Other case studies showed energy savings of 20% at full-load and 55% at a load of 50%. An office building in Southern California replaced two 40-ton chillers with one 80-ton Turbocore unit and achieved an energy savings of 32% over a six-month operating period.

The new magnetic bearing/PM motor technology is more efficient under most circumstances. For an application that is operating at a nearly constant full load condition, the installation would not necessarily benefit from the variable speed, part load increase in efficiency. In their Promising Technologies Evaluation, FEMP states that magnetic bearing variable speed centrifugal chillers have been shown to reduce energy consumption by 42% compared to a standard rotary screw chiller. The magnitude of the savings is dependent upon demand profiles the type of unloading controls incorporated into the chiller design.

Energy Use of Emerging Technology:

5.2 kWh per square foot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 2,007,368,400
Comments:

This technology could technically be used for conditioned space in virtually any commercial building, so we are using the total of the entire commercial building stock in the Northwest. The numbers are taken from preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January, 2014) multiplied times the percentage of commercial space that is conditioned based on the 2009 CBSA. This number is further multiplied by 74% to reflect space cooled by central systems using air-cooled or water-cooled chillers. Subtracted out is the percentage of space cooled by heat pumps and room air conditioners (Navigant Consulting, 2014 Appendix A, P-60).

While these Turbocore units are available in ranges from 60 to 90 tons, multiple units can be combined to meet higher cooling loads.

Commercial Floor Space Appropriate for Chillers with Magnetic Bearings and High-Speed Permanent Magnet Motors

	Total Floor space	% Conditioned	Applicable Space	% Cooled by Central AC and by Air or Water Source Chillers (74%)
Source	(NEEA, 2014)
	3,118,000,000	87.0%	2,712,660,000	2,007,368,400

Regional Technical Potential:
4.46 TWh per year
509 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $1.44
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $0.00

Comments:

The installed cost for retrofits should be in the range of $550 to $600 per ton of cooling. The cost for new chiller installation as well as energy savings and simple payback is presented in two tables available at the links below. As one ton will serve about 400 sf of commercial building space, an upgrading cost of $575/400 sf = $1.44 will be assumed.

Energy Ideas Clearinghouse PTR
http://www.energyideas.org/documents/factsheets/PTR/turbocor.pdf

Daikin McQuay Magnitude™ Chillers
http://www.mcquaybiz.com/Magnitude

Cost Effectiveness:

Simple payback, new construction (years): 7.2

Simple payback, retrofit (years): 7.2

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Reference and Citations:

WSU EEP, 05/12/2006. Product & Technology Review: Turbocor
Washington State University Extension Energy Program

Ben Erpelding, 06/14/2005. Small Oil-Less Centrifugal Compressors: Bringing Energy Efficiency and Reduced Costs to Chiller Plants
ACEEE Summer Study on Energy Efficiency in Industry

Denny Chamberlain, 06/25/2009. NSTAR Technology Show
NSTAR

Navigant Consulting, 05/12/2014. 2014 Northwest Commercial Building Stock Assessment
Northwest Energy Efficiency Alliance

Rank & Scores

PDF

Centrifugal Chiller Compressors with Magnetic Bearings and Variable Speed Control

2015-1 Commercial HVAC TAG (#11)

Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
TAG Ranking: 15 out of 29
Average TAG Rating: 2.95 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:

There are only marginal increases in chiller efficiency. This is not where the big savings are.
There is very little potential for this technology in BPA's territory.
Widely available in a tremendous range of sizes from multiple OEMs. The program Q that I once worked on was how to build a chiller replacement program that would focus on the remaining stock of obsolete, low-efficiency, CFC-refrigerant chillers: modern units get rid of the ozone depletion, much of the GWP, and are almost twice as efficient.
I'd like to see these in more HVAC applications, and I think the technology could be transferred to refrigeration compressor systems, with some research or potential cascade systems.
I think it requires more testing
Much improved efficiency for these type of chillers - heat pump systems eliminate the need for water cooling and water use.

2009 HVAC TAG (#2)

Technical Advisory Group: 2009 HVAC TAG (#2)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary:

The technical feedback form may be used to submit further information about Centrifugal Chiller Compressors with Magnetic Bearings and Variable Speed Control. When possible, please list your references and sources of information.