[BLDG-SIM] Simulation on Thermal Energy Storage using DOE2.2

中原信生 nob_naka at va.starcat.ne.jp
Fri Nov 26 19:44:50 PST 2004


Some comments from Japan.

I have sufficient experience on practical design as well as reserches,
including system simulation and economic analysis on water thermal
storage system. I am consulting for the Heat Pump and Thermal Storage
Technology Center of Japan and compiling manuals on thermal storage
technolgy design, control, maintenance, fault detection and diagnosis.  

First of all, energy efficiency and economy of thermal storage system
are surely verified, only if correct design and control system are
applied. Important points are as follows.

1. Storage tank shall have the pistow flow chacteristics as far as
possible. Several methods are available. (reference at the end)

2. Constant temperature of chilled water, in case of cooling for instant,
shall be output from the chiller to the loweest temperature part of the
tank using either mixing control valve or variable flow rate chiller.

3. Two-way valve controlled VWV system shall be applied to secondary, or
HVAC, water circuit.

4. In case of highrise building, the plate heat exchanger between
the primary circuit and secondary circuit is required, but highly care
shall be taken for the control system not to return low temperature
difference water into the highest temperature part of the tank. 

5. That means, high temperature difference, say more than 10 degree C,
between supply water and return water shall always kept using
appropreate control systems.

6. Optimal control system with daily cooling load prediction algorithm
is recommended to make sure the chiller operation to be shifted to night
as far as possible for part load season.

7. Chiller shall be always operated in full capacity, never to be
operated in part load mode. Capacity control of the chiller shall be
excluded. 

It is of course you must choose as higher COP chiller as possible. In
most case, water-cooled centrifugal or screw chiller is better than
air-cooled chiller.

One more thing I would like to add is that DOE2 as well as other popular
HVAC system simulation programs are not sufficiently able to  reproduce
high efficient thermal storage system as I have mentioned above.

I hope above information is of any use to you. Please refer my papers in
the following, if you are willing to.

N. Nalkahara, et al.: Water thermal storage tank: 
Part 1-Basic design concept and storage estimation for multi-connected
complete mixing tanks
Part 2-Mixing model and storage estimation for temperature-stratified
tanks
ASHRAE Transactions, Vol 94, Part 1.


Ditto: Part 2

ASHRAE TRANSACTIONS

> The last TES I did was for a military base.  I think the base energy manager
> must have gone to a seminar and picked up the buzz word, because he wanted
> TES.  We tried to talk them out of it and just go with a new water-cooled
> central chilled water plant to replace about 10 rotten air-cooled chillers.
> We explained that TES requires the right combination of factors, including
> high demand charge, high peak hour time of use kWh charge, low off peak TOU
> kWh charge, and quite often a utility company or state rebate for demand
> reduction programs to make the project economically viable.  Well they
> wanted their TES and wanted ice storage versus chilled water storage.
> Fortunately, as this was a super ESPC project, the customer was able to kick
> in a few $$ to cover the incremental cost of the ice tanks and associated
> equipment and the rest of the project funded as an energy savings perforance
> contract.  Fortunate, because the electric rates were not conducive to TES.
> Perhaps, the customer saw other value or intangible benefits from the TES.
> 
> As expected, between circulating glycol through the chillers and taking the
> performance hit of recharging the ice tanks with an evaporator temperature
> in the 22 deg.F - 26 deg.F range,kWh consumption during ice charging period
> went up.    In the end, though, the difference in kW/ton between the old
> air-cooled recips with corroded condensers and the new electric screw
> chillers measurement and verification (and the few $ of buydown on the TES
> portion) were sufficient and made for a successful project.  One final note
> of interest.  We ran an analysis with and without the TES and as I recall,
> the TES only contributed a couple of $thousand/year in savings with about
> 98% of the electric savings coming from the improved kW/ton of the electric
> cooling.
> 
> So, don't believe all the buzz words, get the correct rate data and chiller
> part-load data..........and the customer is always right.
> 
> Mike Busman
> Senior Project Engineer
> NORESCO, LLC
> 
> -----Original Message-----
> From: Chris Jones [mailto:cj at cr-jay.ca]
> Sent: Friday, November 26, 2004 10:23 AM
> To: BLDG-SIM at gard.com
> Subject: [BLDG-SIM] Simulation on Thermal Energy Storage using DOE2.2
> 
> 
> We did an analysis of an existing building with a large heat/cool storage 
> system.  The Owners were very surprised to find out that the building was 
> not energy efficient - it just saved on demand charges.  The pumping of 
> fluid in and out of the tanks, through heat exchangers occurred 24 hours a 
> day significantly increasing the kWh beyond that of a conventional hydronic 
> heat/cool building.
> 
> At 01:26 11/26/2004, you wrote:
> >Dear Martin,
> >I think the findings may be correct.
> >First, for a TES system the leaving chilled water temperature usually will 
> >be lower, so the COP will be deduced, but as the outside temperature is 
> >lower, it does not deduced alot.
> >Second, if the TES system using brine water, i think the efficiency will 
> >reduce more.
> >As our experience in some project in Hong Kong and Mainland, TES system 
> >can only reduce electricity cost due to tariff rate rather than
> consumption.
> >I hope these comment would help.
> >
> >Regards,
> >Ernest Tsang
> >Meinhardt (M&E) Ltd
> >
> >
> >Martin Yip <yipch at emsd.gov.hk> wrote:
> >Dear Bldg-sim Subscribers,<?xml:namespace prefix = o ns = 
> >"urn:schemas-microsoft-com:office:office" />
> >
> >I recently simulated an air cooled chiller plant with cold water tank 
> >thermal energy storage using DOE 2.2.  I originally expected some energy 
> >saving due to improve chiller COP at night charging the storage when 
> >compare it with a system without storage.  However, the results showed an 
> >energy penalty of a few percentages even though hourly data actually 
> >showed COP improvement during charging.  I have already set the loss 
> >coefficient to zero for the TES.  I should be most grateful if anyone can 
> >comment on this issue and provide some suggestion.
> >
> >Thanks
> >
> >Martin YIP
> >Engineer
> >EMSD, HKSAR
> >
> >
> >
> >
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> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Chris Jones
> EnerSys Analytics Inc.
> 14 Oneida Avenue
> Toronto, ON M5J-2E3
> Tel. 416 203-7465
> Fax. 416 946-1005  
> 
> 
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