People always ask, what’s so special about Geothermal Ice Rinks vs conventional ice rink refrigeration systems that simply have one function and are designed solely to make ice. Lots to talk about here, but it essentially comes down to what I call the 3 (R’s); Refrigerant safety, Reject heat and Reduced energy.

Historically, a well designed conventional chiller with a good control system that has been sized for the ice rink application, will do a good job of making and maintaining ice, but typically at the expense of waste heat recovery (R1) from the chillers, an obsolete or dangerous refrigerant like ammonia or R22 (R2) and with zero to marginal reduction in energy or conservation in mind (R3).

At GEOIce, we do things differently. (R1) We capture 100% of the reject heat and apply it as free energy in the facilities systems. (R2) We use a very small amount of safety compliant refrigerant R410-A directly in our heat pumps and have the ability to change the refrigerant as mandated. Our circulating refrigerant is ethanol or alcohol -food grade. (R3) Our systems operate with a Coefficient of Performance (COP) of 4 or more, that’s 400% energy efficient.

Understanding that, lets explore Ice Rink refrigeration:

Most ice rink refrigeration systems are based on a typical vapor compression cycle. This is where a compressor is used to create low pressure in a heat exchanger, causing the liquid refrigerant to cool. The cold refrigerant chills liquid that is circulated through pipes in the ice rink floor making ice as water is applied to the floor surface. Energy absorbed from the ice by the chilled liquid is transferred to the cold refrigerant. The refrigerant has an extremely low boiling point and as energy is transferred to the refrigerant it warms to a point of boiling and it becomes a low temperature refrigerant gas. The refrigerant gas then passes through the compressor where it is pressurized and the gas temperature rises creating a hot gas that is pumped through another heat exchanger which is typically located outside as a cooling tower. The heat from the hot gas passing through the cooling tower is expelled to atmosphere/ the outdoor air. After the gas is cooled by the outdoor air or water in the cooling tower, it is drawn through the cycle again to transfer more energy from the ice and the cycle repeats itself 24 hours per day until and if setpoints are satisfied.

Ice rinks use electricity to operate compressor motors, pumps and fans needed to drive the heat from the ice/Ice shed area to the outdoor air. This is done using the compressors to maintain the ice temperature by pulling the heat from the ice surface (and environment of the ice shed area) through the ice and transferring to atmosphere. Typically, there is no balance in the amount of waste heat generated by operations in comparison to the amount of thermal energy drawn from the ice/ice shed. This a general rule and no two ice rinks are the same, depending on the efficiency of the motors, the building envelope, outdoor temperature and numerous other factors.

Ice rink facilities other than in a Pro or advanced setting are typically housed inside a building that has both an ice shed area where temperatures are not controlled as well as a temperature controlled portion. Temperature and humidity of the arena, ice shed area, lobby, offices, locker rooms etc. are controlled by multiple and separate mechanical systems used to provide comfort, domestic hot water, service hot water, etc. These include natural gas/fossil fuel furnaces, rooftop units, boilers, infra red heaters and so on. Humidity is typically controlled by condensing the moisture from the air using a vapor compression system, or by absorbing the moisture from the air using a desiccant wheel and vaporizing it by heating the desiccant with natural gas or other fossil fuels.

Todays energy costs and government requirements have forced conventional ice rink refrigeration systems to look at methods of using some of the energy that is taken from the ice making process as a form of conservation. The challenge is the imbalance in the heating and refrigeration loads required in the building. For example; when the ice is used during the day and evening, occupants, lights and warmer outdoor temperatures reduce the need for heat in the building, but when the rink is used during the colder times of the year or as the sun sets, the refrigeration plant operates much less but the need for heat is greater. This is always a challenge to model and predict accurately, because you are betting against the weather, spectators, hours of sunshine etc.

With conventional systems, thermal energy storage can only capture or hold a portion of the waste heat and the remainder is rejected to atmosphere through a cooling tower.

How we design geothermal ice rinks is completely different. Our GEOIce Heat pumps are designed to extract heat from fluid as low as -4ºF (-20ºC) and as high as 85ºF (29ºC) to make and maintain ice while at the same time, we produce hot water ranging from 80 to 110ºF (27 to 43ºC) which can be boosted to 160Deg F if needed. We operate using the exact same principle as a conventional refrigeration plant. However, using heat pumps capable of operating at such large temperature ranges provides a great deal of design flexibility. We can extract energy from the ice like a conventional ice plant, but can also take energy from other sources like the air or ground while capturing all of the heat that is rejected in the ice production and maintenance. What that means in simple terms, is where a conventional system may have components designed to be 95% efficient, our GEOIce system can in fact operate at a co-efficient of performance of up to 700% when using all of the heat recaptured. Our typical design includes application of heat; in snow melt, flood water, domestic hot water, comfort, pool or spa heating etc., Anywhere we can place the heat we apply it. If we can’t use the heat we store it in the ground for BTU extraction later in the season. What does that mean? Simply put any heat not used is circulated and transferred to the various layers of soil underground through a closed loop system. When making ice we can either use the reject heat or store it in the ground. Typical ground temperatures are found to be approx.. 56 deg F below the surface at various depths depending on latitude. But within a GEOIce geothermal field we may drive the temperatures to exceed 85deg F allowing us to use the heat later in the season through heat transfers described above but in reverse order. This is completed seamlessly and automatically. The three distinct differences or design features in a GEOIce geothermal ice rink that differentiate it from a conventional ice rink system are: (1) A ground source heat exchanger (GHX) or Loop that allows for, (2) Thermal energy storage (TES) below ground and TES storage above ground using tanks. (3) Modular system design that is capable of adapting to both ice and heat production simultaneously in one system for multiple purposes and setpoints.

A GHX/Loop provides a secondary energy source for the heat pumps as well as a thermal battery to temporarily store thermal energy taken from the ice when it can’t be used in the building. The same heat pumps can also extract energy from the GHX/Loop to provide heat for the building even when refrigeration is not needed. Additional heat pumps in other areas of the building, or even in another location, can be connected to the same Loop to provide space heating, service hot water or even swimming pool heating. They can also reject energy to the GHX/Loop and provide air conditioning in the buildings connected to the ground loop/GHX.

A rink slab/floor is designed as thermal mass typically 5 times thicker than the ice. A conventional rink floor is 4-5” thick with a thermal break and 6” subsoil warming system to keep the ice from driving the frost below the slab that creates a permafrost effect causing problems like heaving, cracking or leveling issues to name a few. Not to mention the costs to cure or repair such events. A GEOIce floor is 5-6” thick plus the subsoil warming portion of 12-24” thick (pending rink purpose and size) which provides for large amounts of energy that can be extracted from the lower part of rink floor system without affecting the rink surface temperature immediately. This provides an additional energy source for the heat pumps when the ice temperature is satisfied. The slab and floor system can absorb large amounts of energy during peak use of the ice such as tournament play when the ice is resurfaced several times during multiple hockey games. When the heat pumps are making ice or chilling the thermal storage buffer under the ice, they are simultaneously providing heat for the building. This energy delivered to the building is free in circulation plus avoiding any subsoil issues by controlling the temperature to ambient..

Historical applications of Geothermal in ice rinks provided for the use of multiple heat pumps that could be controlled separately to pull energy from different heat sources (ie. the ice, the thermal storage buffer or the GHX), while they reject recovered energy to either the building or the loop providing a great deal of flexibility. This allowed for one heat pump to provide refrigeration directly to the ice, a second heat pump to sub-cool the thermal storage buffer for a hockey game later in the day, while a third heat pump could withdraw additional energy from the TES to provide full heating capacity to the building if needed. Alternately, all of the heat pumps can work together to make the ice during peak use while only one of them provides the necessary heating components.

GEOIce has changed the face of the ice rink industry with its cutting edge geothermal ice rink designs and the most sophisticated heat pump system available. Fully variable from zero to 100% load applied in a cascade configuration allows the designers to have up to 6 individual heat pumps assigned to separate functions on a priority basis delivering any and all sources of cooling and heat rejection but on standby to be called if one load exceeds its capabilities. Being fully variable allows the system to ramp up or down both the percent of output and performance optimizing energy consumption. As an example, if the system is connected to 3 heat pumps designed to make ice and reject heat for subsoil warming, flood water, DHW , snowmelt for pit or external areas of the building along with pool heat, at any time if there is not enough heat to be provided, the GEOIce system recognizes the call and switches its operation from ice making to hot water to meet the demands of the system. In this application the GEOIce system can deliver up to 160Deg F water if needed delivering the most diversified and automated geothermal system available.