SENECA COLLEGE SCHOOL OF APPLIED ARTS AND TECHNOLOGY

Free CoolingAnd the Earth Rangers Center

TECHNICAL REPORT

Julian Tersigni Building Environmental Systems

17/6/2015

Free Cooling and the Earth Rangers Center

Prepared By: Julian Tersigni

Building Environmental Systems

Air Conditioning and Refrigeration: BES 702

Prepared For: Rafael Raghubir

Acknowledgments

I would like to thank my advisor, Rafael Raghubir for his time and guidance in the completion of this report.

Abstract

The Earth Rangers Center is an environmental charity located in Vaughan, Ontario. The 60,000 ft2 facility integrates innovative energy/water conservation and comfort strategies. This report details free cooling and its use at the Earth Rangers Center (ERC) through geothermal technology.

Table of Contents

Acknowledgments ii

Abstract iii

1.0 Introduction 1

1.1 Purpose 1

2.0 Free Cooling-What is it? 1

2.1 Sources 1

2.2 Prolonged Equipment Life 2

3.0 Free Cooling at the ERC using Geothermal Tech 3

3.1 Installation History 3

3.2 System Set Up 4

4.0 Advantages 5

5.0 Disadvantages 6

6.0 Conclusion 6

Work Cited 7

Pictures Cited 8

1.0 Introduction

A building owner has an increased awareness of energy consumption in their facility whether it is a residential, industrial or commercial property. Globally there is concern over climate change and the role played by energy consumption. The sustainability of a building is an important issue as buildings consume 40% of the world’s total energy use.

1.1 Purpose

This report describes the concept of free cooling and its sources. A specific example of its use is examined through a case study of the Earth Rangers Center, a center for showcasing sustainable technologies. In this facility free cooling is accomplished through geothermal technology. The benefits and disadvantages of free cooling is examined when accomplished through this technology.

2.0 Free Cooling-What is it?

Free cooling is a method to lower the temperature in a building or space by using naturally cooled air or water instead of mechanical refrigeration. 1 With this method the system replaces a chiller in typical air conditioning systems while attaining the same cooling result. It can be used for single buildings or district cooling networks.2

Figure 1: Free Cooling Via Strainer Method1

2.1 Sources

Sources for accomplishing free cooling vary but primarily they are air, water and ground. Air at many elevations can be considerably cooler during certain seasons and times of day than air within a space. By filtering, humidifying and introducing cooler air directly into a space, it is possible to reduce or exclude the use of refrigeration equipment (Figure 1). A source of cold water from a local body of water can be circulated into a space and used instead of undergoing the traditional method of refrigerating a closed water loop with a chiller. A geothermal system (Figure 2) consists of a heat exchange system buried beneath the ground and a mechanical refrigeration equipment component. When operating in free cooling mode the chiller for a building is bypassed and circulates chilled water/glycol from the ground into a space directly through a closed loop or into cooling coils. In all

cases, the industrial cooling systems would only be needed when the outside air or ground temperatures become too high for free cooling systems to be effective. 1

Figure 2: Free Cooling Via Geothermal Loops

2.2 Prolonged Equipment Life

As a result of reduced load on conventional refrigeration equipment, the lifespan on cooling systems can be significantly extended. Reductions in cooling system use (Figure 3) also mean reductions in power consumption and service/repairs, lowering the energy and maintenance costs for facility owners. In reality, free cooling is not completely free. Pumps, fans and other air/water-handling equipment is needed which requires periodic service. 1

Figure 3: Reduced Load on Refrigeration Equipment Extends Lifespan

3.0 Free Cooling at the ERC using Geothermal Tech

The Earth Rangers Centre, located on the conservation lands of the Kortright Center in Vaughan, ON, was built in 2004 as the base of operations for Earth Rangers; a children focused environmental education organization. At 60,000 ft2, the building is LEED-Platinum certified and was built with the mandate to showcase a wide-range of sustainable building technologies and practices one of them being its geothermal system with radiant floor heating/cooling.3

3.1 Installation History

The geothermal system consists of a series of 44 wells, drilled down into sand, gravel, glacial till and finally into shale bedrock beneath the parking lot (Figure 5). Prior to installation of the entire field of wells, a test hole was bored, and a thermal conductivity test was performed to study heat transfer (Figure 4). The test hole showed that the upper 12 meters of the sand layer was unsaturated meaning it would not hold or transfer thermal energy as well as if it were saturated. The water table starts 32 meters below ground level and would be considered part of a high yield aquifer. To test the conductivity of the ground, and thus its suitability for a geothermal system, a 32mm diameter high density polyethylene (HDPE) u-loop pipe was installed in the ground. The test showed that the bedrock improved the thermal conductivity of the site, because the shale has higher conductivity than the load. 4

Figure 4: Geosource Energy Drill Rigs at the ERC

Figure 5: Well Depths and Ground Materials

3.2 System Set Up

The geothermal system at the Earth Rangers Centre was a retrofit installed in 2010 during a parking lot expansion. It is powered by a Carrier 30HXC chiller with approximately 80 tons of nominal heating capacity. The ground loop below the parking lot consists of 44 vertical boreholes going down to a depth of 120 m. The building uses a radiant in-floor/slab distribution system for both heating and cooling. In total there is 22 km of tubing used in the radiant heating and cooling system. High thermal mass reduces peak heating and cooling demand.

When operating in free cooling mode a circulator pump directs the water/glycol mix to a heat exchanger where heat is removed from the secondary interior loop (Figure7). A modulating valve bypasses the chiller and the chilled mixture is circulated through the cooling slabs. In this mode the only electrical consumption is that consumed by the circulator pumps, which is much less than that consumed by the chiller, and the somewhat higher temperatures available when not using a chiller are fine given that the cooling slabs are regulated at higher temperatures anyway so as to be above the dew point.4

Figure 6: Geothermal Manifolds

Figure 7: Geothermal Heat Exchanger with Primary and Secondary Loops and Pumps

4.0 Advantages

Free cooling mode works well at the ERC because of its thermal mass and large ceiling areas used as heat transfer surfaces. The ground temperature in the summer months remains low enough to directly cool the ceiling slabs without the use of refrigeration equipment. In this case study a 60,000 ft2 facility can be cooled with only 18 horsepower in pumping energy.

Refrigeration equipment is needed if humidity levels are high, and the ventilation air must be dehumidified to ensure comfortable air conditions within the building spaces. To date, the heat removed from the geothermal system in the winter has been balanced by the heat removed from the building in the summer. The automation system is programmed to vary how it uses the field to maintain this annual balance. 4

5.0 Disadvantages

Since geothermal energy is not exactly widely used the unavailability of equipment, staff, infrastructure, and training pose hindrance to the installation of geothermal loops in buildings. Not enough skilled manpower and availability of suitable build location pose serious problem in adopting geothermal energy globally. Geothermal energy requires high installation costs as well requiring available land and material to build wells. Geothermal sites also need a recharge period so that in summer when heat is rejected into surrounding earth materials It can cool down again to use for the building. In addition to this wells are inaccessible beneath the ground making repair work difficult with the added risk of damage due to seismic activity in some areas. 5

6.0 Conclusion

Sustainability in a building is critical as it has a large impact on global energy use resulting in impacts on climate change. Facility owners are concerned with allocating monetary resources appropriately with costs saving targets increasing year after year. Free cooling is a successful method of lowering building temperatures in a building and thus it is a huge cost/energy savings tool. Sources for free cooling vary with a geothermal system using earth temperatures for heat exchange. At the Earth Rangers Center the 60,000 ft2 facility can be cooled with only 18 horsepower in pumping energy resulting in huge savings. Geothermal energy is not the most common source of accomplishing free cooling as installation costs are high and a unavailability of equipment, staff, infrastructure, and training hinder its adoption.

Work Cited

1 http://searchdatacenter.techtarget.com/definition/free-cooling2 https://en.wikipedia.org/wiki/Free_cooling3 http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2015/03/GeoExchangeMonitoring_Final_Feb2015.pdf4 http://www.ercshowcase.com/hvac/geothermal/5 http://www.conserve-energy-future.com/Disadvantages_GeothermalEnergy.php

Pictures Cited

Figure1 http://alabamapower.com/business/save-money-energy/energy-know-how/chillers/free-cooling.aspFigure2http://www.ercshowcase.com/wp-content/uploads/2012/11/geosource-visual.jpgFigure 3. http://www.archiexpo.com/prod/carrier-commercial/product-49317-411227.htmlFigure 4. http://www.ercshowcase.com/wp-content/uploads/2012/11/geosource-visual.jpgFigure 5. http://www.ercshowcase.com/wp-content/uploads/2012/11/geosource-visual.jpgFigure 6. http://www.ercshowcase.com/wp-content/uploads/2012/11/geosource-visual.jpgFigure 7. http://www.ercshowcase.com/wp-content/uploads/2012/11/geosource-visual.jpg