Energy efficiency model for small/medium geothermal heat pump systems

(ProQuest: ... denotes formulae omitted.)IntroductionFinding reliable energy sources and increasing energy efficiency are two of the most important challenges facing humankind. Dependency on energy, environmental harm and climate change are central problems human beings must solve (IPCC, 2014; Bohm, 2010; IEA, 2013; Edenhofer, 2011; Rogall, 2000; Crowley, 2000). Rising energy costs and increasing concern for environmental stewardship over the past 20 years have inspired interest in an old technology first invented in the 1860's (Zogg, 2008). HP is currently used in heating technology using a RES to reduce greenhouse gases, energy costs and dependency on fossil energy sources. After the first energy crisis in the 1970's (Yergin, 2008; Inkenberry, 1986; Merril, 2007), HP technologies were developed further. Due to lower energy prices and technical difficulties after the crisis, these technologies made up a small minority of the market until the beginning of 1998. Because of higher energy costs and dependencies on fossil fuels from 1998 until today, HP sales have steadily increased (Nowak, 2013; Bayer, 2012). New ideas and innovation in HP technology increase the efficiency of the different HP devices (Park, 2014, 2013; Jeong, 2014; Wang, 2015; Staiger, 2004, 2005, 2006, 2014; Sanchez, 2014).More than 40% of the thermal energy demand in the EU (EU 2014, 2010a, 2010b; BMU, 2012) is used for heating. There is a huge potential in saving energy through new energy efficient heating technology. This is one reason that EU directives (EU 2012a, 2012c, 2009, 2013a) clearly define for all member states how buildings should be designed and built, how heating systems should be implemented with RES and how new heating appliances should have increased energy efficiency. In the last 10 years, use of HP technologies has increased over 60% in the EU (Nowak 2013; Rees 2014).Small heat pump systems are up to 10 kW and medium heat pump systems are up to 25 kW. With these sizes of HP devices, new low energy buildings (comercial and private) with up to 500 m2 surfaces and domestic water could be heated. Efficiency of small/medium size GHP corresponds to 200-380% depending of the type of HP and the entire HP system boundaries. This means that for each kW of electrical consumption, 3kW to 4,8 kW of thermal energy are generated. About 75% of the energy that is used in a GHP is renewable, whereas 25% of the energy is generated by other sources (in 99% of the cases this is electricity). If the electricity for the HP is generated from renewables (PV, wind, hydro, biomass etc.) then the HP system is 100% renewable and CO2-neutral. In comparison to today's heating technologies, Figure 1 shows the average Max/Min efficiencies.There is a variety of HP's on the market (see Table 1). There are three main types. The first type is a HP which takes energy Qrenew out of the soil (GHP) (Konigsdorff, 2011; Schroder, 2012). The second type is a combination with other RES such as thermal solar, waste water and others (hybrid systems) (Miria, 2013; Mojic, 2014). Third type is a HP where the Qrenew will be taken out of the air (air/water HP) (Konigsdorff, 2011). Today's HP technology can be used for heating and cooling (passive and active cooling). Hybrid means "mixed" and combines two energy systems with the aim of achieving ecological and economic sense to satisfy the total heating and cooling demand of a building. The combination possibilities for hybrid heat pumps are varied. The main advantages and disadvantages of HP Types are presented in Table 2.HP manufacturers, HP sales companies and HP installers use efficiency as the most important criteria in the sales and marketing process. The EU energy label will be the most important selling point for heat pumps in the future (BWP, 2015; EHPA, 2013; Rasmussen, 2011; EU, 2013b).Theoretical energy efficiency for technical and economic HP modelsThe energy efficiency for a technical HP model can be explained using the Carnot cycle process (Cube, 1997; Baehr and Kabelac, 2006; Miara, 2013; Reisner, 2013; Tiator, 2014; Tonert, 2013). …