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01 | 2013 Free cooling guide CO O LING INT EGR AT ION IN LOW- E N ERGY H OU SES

01 | 2013 Free cooling guide CO O LING INT EGR AT ION IN LOW- E N ERGY H OU SES Table of contents 1. Introduction to the concept of free cooling ...3 The need for cooling in low-energy houses .............4 Comfort and energy efﬁ ciency – the best ﬁ t for low-energy houses ............................................4 Investing for the future – the design of a low-energy house ...................................................5 2. Cooling loads in residential buildings .............6 Factors inﬂ uencing the sensible cooling load ..........6 Factors inﬂ uencing the latent cooling load .............7 The effect of shading ..............................................7 Room variation .......................................................8 Duration of the cooling load ..................................8 Required cooling capacity .......................................9 3. The ISO 7730 guidelines .................................10 Optimal temperature conditions ............................10 Draught rate .........................................................11 Radiant asymmetry ...............................................11 Surface temperatures ............................................12 Vertical air temperature difference ........................12 4. Capacity and limitations of radiant emitter systems ..............................................13 Heat ﬂ ux density ...................................................13 Thermal transfer coefﬁ cient ..................................13 Dew point limitations ............................................13 Theoretical capacities of embedded radiant cooling ......................................................14 5. Ground heat exchangers .................................15 Ground conditions ................................................15 Ground heat exchangers .......................................16 Ground temperature proﬁ le...................................17 Primary supply temperatures .................................17 Dimensioning of ground heat exchangers for free cooling .....................................................17 6. Free cooling in combination with different heat sources ....................................19 7. Choosing and dimensioning the radiant emitter system ................................................20 Capacity of different radiant emitter systems ........20 Radiant ﬂ oor constructions and capacity ..............22 Radiant ceiling constructions and capacity ...........24 Capacity diagrams .................................................24 Regulation and control..........................................26 The self-regulating effect in underﬂ oor heating ..27 Functional description of Uponor Control System .................................................................27 Component overview ............................................29 8. Uponor Pump and exchanger group (EPG6) for ground sourced free cooling .....................29 Dimensions ...........................................................30 Pump diagram .......................................................30 Control principle ...................................................31 Installation examples.............................................33 Operation of Uponor Climate Controller C-46 .......36 Operation mode of Uponor Climate Controller C-46 .....................................................36 Dew point management parameters and settings .................................................................37 Heating and cooling change-over: external signal .......................................................38 Heating and cooling change-over: Uponor Climate Controller C-46 ............................38 2 UPO NO R · FRE E CO O L I NG GUIDE 1. Introduction to the concept of free cooling Free cooling is a term generally used when low external temperatures are used for cooling purposes in buildings. This guide presents a free cooling concept based on a ground coupled heat exchanger combined with a radiant heating and cooling system. A ground coupled heat exchanger can for example be horizontal collectors, vertical boreholes or energy cages. A radiant system means that the ﬂ oors, ceilings or walls have embedded pipes in which water is circulated for heating and cooling of the building. Under ﬂ oor heating and cooling is the most well know example of a radiant system. A radiant system combined with a ground coupled heat exchanger is highly energy efﬁ cient and has several advantages. In the summer period, the ground coupled heat exchanger provides cooling temperatures that are lower compared to the outside air. The radiant system operates with large surfaces, which means it can utilize the temperatures from the ground directly for cooling purposes. The result is that free cooling can be provided with only cost being the electricity required for running the circulation pumps in the brine and water systems. No heat pump is required. In the heating season the system is operated using a heat pump. As the ground temperature during winter is higher compared to the outside air temperature, the result is improved heat pump efﬁ ciency (COP) compared to an air based heat pump. In addition, the radiant emitter a system (under ﬂ oor heating) operates at moderate water temperatures in large surfaces which further improves the heat pump COP. 3 U PON OR · F R EE CO O L I N G G UI DE The need for cooling in low- energy houses Today, there is a high focus on saving energy and utilising renewable energy sources in buildings. The energy demand for space heating is reduced by increased insulation and tightness of buildings. However, increased insulation and tightness also increase the cooling demand. The building becomes more sensitive to solar radiation through windows and becomes less able to remove heat in the summer. More extreme weather conditions further contributes to the cooling needs and together with an even more increased consumer awareness of having the right indoor climate, the need for cooling also in residential buildings will become a requirement. Optimal architectural design and shading will help to reduce the cooling need, but simulations and practical experience show that such measures alone will not eliminate the cooling need. Space cooling is needed, not only in the summer, but also in prolonged periods during spring and autumn when the low angel of the sun gives high solar radiation through windows. In order to meet the energy frame requirements of the building regulations, space cooling can be provided by utilising renewable energy sources such as ground heat exchangers for cooling purposes in conjunction with a radiant system with embedded pipes in the ﬂ oor, wall or ceiling. Cooling needs will differ between rooms and are highly inﬂ uenced by direct solar radiation. Rooms with larger window areas and facing the south will generally have higher cooling requirements. In periods with high cooling loads, active cooling is normally required during both day and night time. Comfort and energy efﬁ ciency – the best ﬁ t for low-energy houses Using shading will help to reduce the cooling demand. However, this forces occupants to actively pull down the shades e.g. when leaving the house. Also, shading will block daylight which increases electricity consumption on artiﬁ cial light, and shading will block the view which may not be in the interest of the home occupant. In fact many architects state that energy efﬁ ciency and comfort may conﬂ ict when deﬁ ning comfort in a broader sense, such as the freedom to design window sizes, spaciousness with increased ceiling height, daylight requirements and the occupant’s tendency to utilise open doors and windows. All such requirements put increased demands on the HVAC applications. Ground heat exchangers combined with radiant systems is the only “all-in-one” solution, with the ability to provide both heating and cooling. Such systems are more cost efﬁ cient and simpler to install than having to deal with a separate heating and cooling systems. Furthermore, radiant systems are able to heat at a low supply temperature and cool at a high supply temperature. This ﬁ ts perfectly to the typical operating temperatures of a ground coupled heat exchanger. Furthermore, the connected heat pump will be able to run more efﬁ ciently and thereby consume less electricity. In addition, a radiant system provides no draught problems and provides an optimal temperature distribution inside a room. Last but not least, radiant systems provide complete freedom in terms of interior design, as no physical space is occupied inside the room. Even more important when looking at the lifetime and property value of a house, such systems have very low maintenance need and a lifetime that almost follows the lifetime of the building itself. In today’s uncertain environment of future energy prices, free cooling and ground coupled heat pumps provides a high stability on the future energy costs of the building in question. It will most certainly meet today’s and future building regulations even in a scenario where future property taxation would be linked to energy efﬁ ciency. Hence, it is an investment that helps to maintain and differentiate the future property value. 4 UPO NO R · FRE E CO O L I NG GUIDE Investing for the future – the design of a low-energy house A radiant system, e.g. underﬂ oor heating and cooling, coupled to a ground source heat pump, provides optimal comfort with high energy efﬁ ciency both summer and winter. In addition, due to the increased tightness requirements in low-energy houses, a ventilation system is necessary to maintain an acceptable indoor air quality. In order to keep the ventilation system energy efﬁ cient, it should be coupled to a heat recovery ventilation (HRV) unit to minimise heat losses through the air exchange. Energy sources for cooling There are several alternative HVAC applications available for cooling purposes. A district heating connection is an energy efﬁ cient option for space heating, but cannot be used for cooling purposes. Alternative means of cooling could be an air-to-water heat pump, but no “free cooling” can be extracted from such a system, hence cooling can only be provided with the heat pump running causing a higher electricity consumption. Purely air-based systems like split units can also act as a cooling system but as can be seen from the picture below, the efﬁ ciency is considerably lower than for water-based cooling systems. European seasonal energy efﬁ ciency ratio (ESEER) for different cooling systems. ESEER is deﬁ ned by the Eurovent Certiﬁ cation Company and calculated by combining full and part load operating conditions. Correlation between average property m2 prices and energy class The ﬁ gure above shows the correlation between property prices and the energy efﬁ ciency level of the property in Denmark. uploads/Geographie/ free-cooling-guide.pdf