Economic Evaluation of New-type Energy Geo-structures in Residential Buildings. A Case Study in Moderate Mediterranean Climate
Date Issued
June 2022
Abstract
Shallow Geothermal Energy Systems (SGESs) are Renewable Energy Systems (RES), which are
applied in the residential sector through the use of Ground Source Heat Pumps (GSHPs). GSHPs
are coupled with Ground Heat Exchangers (GHEs), where heat is absorbed or rejected through a
network of pipes in the ground. GSHPs have not yet thrived in the RES market because of their
high initial costs and long payback periods.
Two Energy Geo-Structure (EGS) systems, in specific the foundation (or energy) piles and the
foundation bed of a residential building in moderate climate Mediterranean conditions in the island
of Cyprus, were computationally modeled by Aresti et al. [1]. A theoretically typical house with
nearly Zero Energy Building (nZEB) characteristics was examined, with estimated heating and
cooling loads used as inputs to investigate the performance of the EGS-GSHP systems. Both
systems were shown to exhibit steady performance and high Coefficient of Performance (COP)
values, making them an alternative RES solution for integration in residential building.
In this study the above-mentioned systems were evaluated economically by comparison with a
conventional high- and low-performance Air Source Heat Pump (ASHP) systems. Although
various methods could be used to evaluate the economic benefits of the systems, to simplify the
study, only the difference in the cost of the two systems is used here through the Simple Payback
Period (SPP) and the Discounted Payback Period (DPP) methods. The monthly loads and average
monthly COP values of each system, as well as the lifespan and the cost of the HP replacement
were considered. It is noted that the costs related to grout filling and the borehole extraction are
not included, as in any case the buildings foundations would be constructed, therefore no cost is
added. The cost of the HPs was based on the local market (as of year 2020) at EUR8500 for a high efficiency ASHP, EUR4500 for a low-efficiency ASHP, and at EUR6500 for a GSHP.
applied in the residential sector through the use of Ground Source Heat Pumps (GSHPs). GSHPs
are coupled with Ground Heat Exchangers (GHEs), where heat is absorbed or rejected through a
network of pipes in the ground. GSHPs have not yet thrived in the RES market because of their
high initial costs and long payback periods.
Two Energy Geo-Structure (EGS) systems, in specific the foundation (or energy) piles and the
foundation bed of a residential building in moderate climate Mediterranean conditions in the island
of Cyprus, were computationally modeled by Aresti et al. [1]. A theoretically typical house with
nearly Zero Energy Building (nZEB) characteristics was examined, with estimated heating and
cooling loads used as inputs to investigate the performance of the EGS-GSHP systems. Both
systems were shown to exhibit steady performance and high Coefficient of Performance (COP)
values, making them an alternative RES solution for integration in residential building.
In this study the above-mentioned systems were evaluated economically by comparison with a
conventional high- and low-performance Air Source Heat Pump (ASHP) systems. Although
various methods could be used to evaluate the economic benefits of the systems, to simplify the
study, only the difference in the cost of the two systems is used here through the Simple Payback
Period (SPP) and the Discounted Payback Period (DPP) methods. The monthly loads and average
monthly COP values of each system, as well as the lifespan and the cost of the HP replacement
were considered. It is noted that the costs related to grout filling and the borehole extraction are
not included, as in any case the buildings foundations would be constructed, therefore no cost is
added. The cost of the HPs was based on the local market (as of year 2020) at EUR8500 for a high efficiency ASHP, EUR4500 for a low-efficiency ASHP, and at EUR6500 for a GSHP.
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