Underfloor Air Distribution and Radiant Heating/Cooling: Innovative Applications of Geothermal HP Systems in Schools

STEPHEN HAMSTRA, P.E., HBDP, LEED AP, CGD

IGSHPA Technical ConferenceGrapevine, TexasOctober 22, 2009

Why?

Reduce operational costs – free up $$$ for education

Community Credibility – show good stewardship

Attract students/families and retain staff

Funding opportunities – donors like “green” projects

Case Study: Existing Elementary School•Retrofit Geothermal Heat Pump Project

•Replacing Existing Gas Boiler/Classroom Unit Ventilators

•Ventilation Energy Recovery built into Unit Ventilators

•Adding cooling

Jamestown Elementary Site Plan

Floor Plan

New Exterior Elevations

Mechanical Floor Plan

Heat Pump Unit

Unit Ventilator Replacement

Lessons Learned:•Geothermal Heat Pump Unit acoustics are important!

•Connections to outside air louvers – special attention to sealing

Jamestown Elementary

The “Flux Capacitor” Concept

What does time travel have to do with Geothermal Heat Pump Systems?

GeoExchange Systems can “store” massive amounts of energy (like a “flux capacitor”) giving us a thermal flywheel effect

GeoExchange Systems can “time shift” that energy

Heat Dissipation/Absorption

GeoExchange Heat Transfer

Solar Radiation

Conduction/Convection/Radiation at surface

Conduction to surrounding soil

Ground Water Movement

1 Gigawatt-hour = 3.4 Billion BTU-hours

Typical 1,000 ton capacity system:

150,000 borefeet at 20 feet on center

Control volume of 60 million cubic feet of soil

At 100 #/CF density => 6 billion pounds

At 0.35 BTU/ degree F Specific Heat we get:

2.1 Billion BTU’s stored per one degree F

To store 1.21 Gigawatt-hours we need only change the soil temperature by 1.6 F!

If the annual temperature swing for this system was 30 F, we would be “storing” more than 22 “gigawatts!”

Heat Dissipation/Absorption

Combining Mixed Use Buildings on Common Loop

THE ENERGY CHASSIS CONCEPT Pioneered by GMB A+E

Geo HX In

Geo HX Out

Geo HX In

Geo HX Out

CHWR In

CHWS OutHWS Out

HWR In

VVP VVP

Extended Range Heat Pump Chiller

Operating Modes:

1. Heat recovery - make chilled water and hot water simultaneously

2. Chilled water – make chilled water and reject heat to geothermal HX

3. Hot water – make hot water and absorb heat from the geothermal HX

THE ENERGY CHASSIS CONCEPT Pioneered by GMB A+E

Case Study: New Elementary School•Central Plant Geothermal Energy Center

•Displacement Ventilation System – 100% Outside Air/No Recirculation

•Radiant ceiling cooling

•Radiant floor heating

•Net annual energy consumption 50 kBTU/SF/year

Georgetown Elementary School Site Plan

TOTAL SQUARE FOOTAGE

Footprint : 66,765

Mezzanine: 2,071

Total: 68,846

Floor Plan

Radiant Cooling Panel

Concept Diagram for Ventilation

Mechanical Floor & Site Plan

Geothermal System Floor Schematic

To effectively apply advanced concepts we need to have advanced simulation tools for design.

SIMULATIONS ARE IMPORTANT

Radiant Cooling Panels and Displacement Diffusers

Sp1

65.2

76.2 °F

70

75

FLIR Systems

Sp1

65.7

76.6 °F

70

75

FLIR Systems

Thermal Images

Radiant Cooling Panels

Radiant Floor Heating

Lessons Learned:•Control deadbands are important – Clients can be hard to control…

Georgetown Elementary

Case Study: New Elementary School•Central Plant Geothermal Energy Center

•Displacement Ventilation System – 100% Outside Air/No Recirculation

•Underfloor (raised floor) Air Distribution System

•Thermal mass energy storage

•Net annual energy consumption 35 kBTU/SF/year

Quincy Elementary

Typical Classroom

Cafetorium

Media Center

Raised Access Floor - Diffusers

Raised Access Floor – Floor Power/Data Outlet

Geothermal Borefield- Loop Manifolds

Central Plant Geothermal Heat Pumps

Lessons Learned:•Give yourself some room with regards to capacity and performance at high condenser water temperatures – don’t live life on the edge!

•Thermal mass can work with you or against you – think about it when developing control sequences.

Quincy Elementary

Conceptual Net Zero Energy School

Can we create Net Zero Schools?

• Optimized Building Envelope

• Daylight Harvesting Systems

• Advanced Lighting Controls

• Earthtubes

• Solar-Reactivated Cooling

• Radiant Chilled Ceilings/Chilled Beams

• Radiant Floor Heating

• Displacement Ventilation

• Hybrid Geothermal Heat Pump System

• Solar Domestic Hot Water Heating

• Ventilation Energy Recovery Systems

• Potable Water Use Reduced by 90% through Rain Water Harvesting and Low Flow Fixtures

• Solar Photovoltaic (PV) System for Electrical Generation

• Wind Turbines for Electrical Generation

Yes it can be done! And not just schools…

Whole Building Design

Whole Neighborhood/Campus Design

Whole Community Design

Design Philosophy (everything connects to everything…)

Classical engineering training says “solve problems one at a time”.

Design Philosophy

We say “NO!”

This is partly how we got into the challenging position we are in today – we’ve solved

problems without first considering the solution in a larger context.

Consider:

(in order of importance)

1. Reduce the loads, reduce the loads, reduce the loads…

2. Recover wasted energy wherever you can

3. Find ways to reuse waste energy

4. Consider innovative energy systems (geothermal heat pumps)

5. Consider renewable energy systems

6. Measure, verify, learn, improve, repeat…

Design Philosophy

THANK YOU!

steveh@gmb.com

www.gmb.com

STEPHEN HAMSTRA, P.E., HBDP, LEED AP, CGD

Executive Vice President