San Francisco Transamerica Pyramid installed Co-Generation System

BB. · August 2013

An interesting article... Some large utility customers are installing full blown Co-Generation systems that can supply 70% of the electricity and 100% of the heating/domestic hot water needed for a large office building.

San Francisco: PG&E Commercial Customers Get Inside Look at What Powers Transamerica Pyramid

At $4 million, the system, also known as a co-generation system, isn’t cheap. But it will pay for itself by 2014, about five years after it went online, saving the building about $700,000 a year in energy costs.
...
To date, the Transamerica Pyramid has received almost $1 million in rebates for its self-generation system and energy-efficiency programs, which include a current Energy Star rating of 98.
...
Running a co-generation system takes dedication. Peterson has a maintenance crew of seven employees who work 24 hours a day, five days a week.
...
Peterson said he’s currently in the process of replacing two pieces of equipment—piping that wasn’t braced properly to handle the thermal dynamics of the hot water and heating exchangers that don’t adequately handle high water pressures for the building. Those two pieces of equipment will cost more than $200,000 and delay the payback date.
...
Despite any drawbacks, the project has resulted in energy savings of 4.5 million kilowatt hours a year. The Transamerica Pyramid is also among the top 2 percent of energy-efficient commercial office buildings in the United States.

I guess it is a V12 natural gas fueled, turbo charged genset. Photo (from this PDF report).

Attachment not found.

-Bill

Panamretiree · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

Without the $1M in subsidies, I wonder if Transamerica would have put in the system.

Heat recovery from exhaust systems is an excellent way to recoup energy. Heat recovery units have been around since the late 60s and early 70s, maybe even earlier; however, very dependent on ultra clean fuel - NG is great, but distillate, #2 stove oil or straight diesel is not the best to use, too much carbon residue - plugs up the heat exchanger unless sized properly, and needs constant cleaning.

The main benefit to this system is it is a dedicated power source for a specific enterprise; however, if the company is purportedly saving money, is there a payback to the consumer, or is the cost of the install being transferred to the consumer? I would think that there is no free lunch here and regardless of how you spin this, someone is paying for the install.

JMHO.

Cheers

Ernest

BB. · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

I would like to hear from you Ernest or Chris Olson about Natural Gas generator installations...

I understand the "cheap and dirty" way of using NG is to have a diesel engine and just start feeding NG into it--The engine will cut back on the diesel to maintain RPM. More NG, less diesel needed.

How is a pure NG installation operated (in diesel cycle with injectors/compression ignition, or something else)?

I would guess that most of the heat is from the water jacket/oil cooling. The exhaust probably does not have much "useful heat" after running through the turbo chargers.

-Bill

Panamretiree · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

Not having used NG in any prime movers, I will defer to a better authority. I would suspect that diesel technology has had to adapt for NG use much like cars and unleaded fuel. The diesels and gas turbine generators I have operated (1000 kW diesel units and 750 kW gas turbine units) were always fueled with naval distillate.

Having been involved with heat recovery systems on our naval ships, I can state that during the design phase, heat exchangers worked quite well, but the fuel used during this phase was NG, not naval distillate. This proved to problematic because the design for a distillate system is considerably different than from an NG system because of the cleanliness of the exhaust, more carbon/soot residue from distillate/diesel fuel that requires greater tolerances in the heat exchanger (slight oversight from our design engineers). Our navy finally took the heat exchangers out because it was more trouble than it was worth to try and keep these units operating.

You can get a considerable amount of heat from a diesel exhaust, but there has to be a balance because too much cooling and you run the risk of condensing the exhaust gases to the point where you have condensation in the exhaust system and with this, maintenance issues. The distance the exhaust travels is also an issue.

I would surmise that a heat recovery system using diesel exhaust could be part of the system, could be heat recovery from water jacket/oil cooling and there are electric hot water tanks throughout the structure. Not a lot of detail in the articles, but would be interesting to find out how it is put together.

This probably did not answer your question, but it is the best I can give with the information available.

JMHO

Cheers

Ernest

peakbagger · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

What they didnt mention is that there was a gas fired cogen system installed in this building about 7 years ago. The company I worked for designed and installed it. At the time the reason for doing it was that the building was on a very cost central heating and cooling district, plus they were marketing it for companies that needed critical power access. We also had at one of these systems in NYC.

As far as i know, the large natural gas engines we used were spark ignition engines. NG has a fairly high octane rating so the engines are higher compression that a gasoline engine. There are compression ignition diesels that can use supplemental natural gas. Permitting standby engines in general is quite difficult.CA laws are extremely stringent even with state of the art emission controls the numbers are so low for NOX that few suppliers would guarantee they would meet the numbers.

There are a couple of options for heat recovery. The exhaust heat can be used to generate additional electric power using an organic rankine cycle or a waste heat recovery boiler and a steam turbine. This produces a lot of low grade heat good for space heating or cooling. Absorption cooling is a nice way to get rid of waste heat, single effect coolers have low inlet temps but lousy efficiency, double effect units are more efficient but require higher inlet temps. There is also a small waste heat stream from the units oil coolers, many installations dont recover this. These systems have to be equipped with a lot of ways to reject heat, frequently cooling towers or wetted surface units.

Panamretiree · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

Peakbagger - as you mention, the article is short on specifics, but it is spun to sound good. Your definition of a gogen system, using one form of power to generate another is also my understanding, heat recovery or production is a by-product.

It would still be nice to see the design of the system.

BB. · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

I did try to find a more technical article--But this was the best I could find after a few minutes of looking.

-Bill

Panamretiree · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

BB - not a problem. News is very much in the eye of the presenter and what they wish to convey. Regardless of history or what is stated, the mere fact that a business is installing a "green" initiative is always good.

SkiDoo55 · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

Here is some more on the install from published news article;

Northern Power's CHP system will consist of two 560-kW natural gas-fired reciprocating engine generators, which will operate in parallel with the utility's downtown network grid. The two generators are designed to provide approximately 70% of the electrical requirements of the 530,000 square foot commercial office building. Recovered waste heat from the engines will be used to heat the building, displacing 100% of the steam currently purchased for heating purposes. Additionally, waste heat will drive a 320-ton absorption chiller that will be installed to create chilled water for the building

BB. · August 2013

Re: San Francisco Transamerica Pyramid installed Co-Generation System

Yep, downtown San Francisco still has steam heat available from two power plants:

http://www.nrgthermal.com/centers/sanfran/syssf.htm

NRG Thermal has owned and operated San Francisco’s district energy system since 1999. The system was established in 1930 when local utility Pacific Gas and Electric Co. (PG&E) purchased three steam electric plants from Great Western Power Co. In 1993, PG&E sold its district heating operations to Thermal Ventures Inc., which formed a subsidiary, San Francisco Thermal, to operate the system. In 1995, NRG Energy Inc. acquired 49 percent of San Francisco Thermal. During the late ‘90s, the system experienced remarkable growth, adding nearly one new customer a month for a number of years, leading to NRG Thermal’s full purchase of what is now NRG Energy Center San Francisco.

Services provided: Steam for space heating, domestic hot water, air conditioning and industrial processes. The Energy Center also assists customers with equipment repair, upgrade, expansion and maintenance, as well as preparing multiple-year energy budget forecasts.

Area served: 2 square miles of downtown San Francisco's central business district..

Buildings on system: Approximately 170.

Building space served: More than 37 million square feet of space.

Total system capacity: 410,000 lb/hr of steam.

Annual production: 700 million lb of steam.

Plants:
Station T. Located at 460 Jessie St. Houses six boilers: two produce 55,000 lb/hr of steam; two produce 100,000 lb/hr; one produces 50,000 lb/hr; and one produces 82,000 lb/hr. All boilers are fueled 100 percent by natural gas; No. 2 diesel is available as a backup fuel on some units.
Station S. Located at 1 Meacham Place. Equipped with three boilers: one in operation producing 65,000 lb/hr of steam and two that are installed and permitted but not currently in use. All boilers are fueled 100 percent by natural gas.

Distribution network: 10 miles of underground steam piping.

-Bill

San Francisco Transamerica Pyramid installed Co-Generation System

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