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

[中原信生]

Sorry I forgot to identify myself.

Nobuo Nakahara
Prof. Emeritus, Nagoya University
Nakahara Laboratory, Environmental Syst.-Tech. (NESTEC)
20-48-2, Harusatocho, Chikusaku, 
Nagoya 464-0038
Tel: +81-52-759-1638, Fax: +81-52-759-1639
Email: nob_naka at va.starcat.ne.jp
URL:  http://www2.starcat.ne.jp/~nob_naka/

> 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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