Lecture Objectives: Learn about thermal storage systems Discs pumps and plumbing

Thermal storage for adjustment production to consumption We need a thermal storage somewhere in this system !

Example problem

Thermal storage Store heat Store cooling energy Many issues to consider (∆T, pressure, losses,…. ) Store cooling energy Chilled water For cooling condenser For use in AHU (cooling coils) Ice storage Compact but… Other materials (PCMs) that change phase the temperature we need in cooling coils Many advantages, but disadvantages too!

On-Peak and Off-Peak Periods This profile depends on the type of building(s) !

Chilled water tank Use of stored cooling energy Store Use

Which one is better ? Depends on what you want to achieve: Peak electric power reduction Capacity reduction …..

Downsizing the Chiller Lower utility costs Lower on-peak electrical consumption(kWh) Lower on-peak electrical demand (kW) Smaller equipment size Smaller chiller Smaller electrical service (A) Reduced installed cost May qualify for utility rebates or other incentives

Sizing storage system (use Annual Cooling-Load Profile) How often you need to use it? What are the cost-benefit curves ? What is the optimum size ?

Ice Storage Tank Many issues ! …. As freezing progresses progress the ice becomes thicker and significantly impedes heat transfer

Open Ice Storage Tank Also issues ! …..

Fluid Flow Rate and Freeze ΔT

Impact on Chiller Efficiency

PCMs A. Sharma et al. / Renewable and Sustainable Energy Reviews 13 (2009) http://www.docunator.com/bigdata/1/1367142535_c566e7d75e/reviewexample2.pdf

Other latent heat thermal storage systems (research is ongoing)

Construction and benefits Active Passive (wall)

Stratified chilled water tanks

Temperature and dynamics Temperature at outlet during the changing cycle of the tanks

Stratified chilled water tanks diffuser geometry Challenge: “Pull” large amount of energy without disturbing stratification

Modeling Write energy and mass balancer equation for each section

Installation of thermal storage system Upstream Downstream • Increases chiller efficiency • Increases chiller capacity • Overall system efficiency ??? • Decreases storage capacity • Simplifies system layout • ….. • Decreases chiller efficiency • Decreases chiller capacity Overall system efficiency ??? • Increases storage capacity •…… • Does not allow chiller shut down!

Plumbing - System Curves A+B A B A+B A B V A B V A B Parallel Serial

System balancing AHU1 AHU2 HC1 HC2 100 ft 1000 ft 10 gpm 2 gpm 10 ft pump BOILER

Pumps Raise pressure and produce flow Main type Centrifugal Example of Turbine pump Base mounted Reading (textbook) Page 3-36 - 3-45 Inline http://www.taylor- engineering.com/downloads/cooltools/EDR_De signGuidelines_CoolToolsChilledWater.pdf

Curve for Multiple Pumps

Changing Pump Speed

Primary/Secondary and Tertiary Pumping Reading Assignment: Taylor, S., P. Dupont, B. Jones, T. Hartman and M. Hydeman. 2000. Chilled water plant design guide. San Francisco: Pacific Gas & Electric Company. http://www.taylor- engineering.com/downloads/cooltools/EDR_DesignGuidelines_C oolToolsChilledWater.pdf

Hydronic systems for district cooling/heating and buildings Constant-Flow System, Single Chiller, Single Coil Constant-Flow System, Single Chiller, Multiple Coils Mixing valve that control by-pass flow Major pumping force is the chiller pump

Control of coil temperature Mixing valve that control the flow through the coil Flow Variation as a Function of Valve Position Same pressure drop like a cooling coil Major pumping force is the chiller pump

Multiple chiller (or boilers) Parallel Serial

Primary-Loop Only Variable Speed Flow Single chiller Multiple chillers

Primary and Secondary Loop Variable Flow Design Parallel chillers Serial chillers

Large Plant or Building Distribution Systems Primary/Secondary Loops with Variable Flow and Distributed Pumping

Primary/Secondary and Tertiary Pumping

Primary Pump Arrangements Dedicate a pump for each chiller Provide a common header for the pumps

Coil Pumping Strategies Variable speed pumps vs. Single pas Valve vs. Mixing valves vs. Diverting Valves

Impact of plumbing on a cooling coil

Plumbing Arrangement in Building’s hydronic systems Radiators Baseboard heaters Fan coil systems

Valves Section 5-14 and 6-15 in the textbook Types Butterfly Valves Ball Valves Globe Valves Three way valves

Valve Sizing and Flow Coefficient Cv value: in liter/hour or…. in Pa Control Valve Selection For Hydronic Systems reference: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCUQFjAA&url=http%3A%2F%2Fbookstore.ashrae.biz%2Fjournal%2Fdownload.php%3Ffile%3Dhegberg.pdf&ei=IvcqU_O1KMuE2AWgloHgDA&usg=AFQjCNFRAMzPnbzDpAluhyk4l8u_SKKTdw

Control Valve Selection For Hydronic Systems Before DC we tried to do this Valve authority