تجزیه و تحلیل انرژی و هزینه یک سیستم میکرو تولید تجدید پذیر هیبریدی در خدمت چند ساختمان های اداری و مسکونی کوچک

This study investigates the energy and cost performance of hybrid renewable ground source heat pump (GSHP) and natural gas fueled fuel cell (FC) microgeneration systems serving multiple residential and small office buildings in Ottawa (Canada) and Incheon (South Korea). The study is performed by simulations in TRNSYS environment. The performance of the microgeneration system is compared to a GSHP only system. In addition, the impact of the FC capacities, natural gas price and electricity price on the system's energy and cost performance is examined. The energy analysis results show that the GSHP–FC systems have less primary energy consumption compared to the GSHP only system in both geographic locations. However, whether a GSHP–FC system could achieve operational cost saving is strongly dependent on the local natural gas and electricity prices and also on the building heating, cooling and electrical loads and their patterns. The GSHP–FC microgeneration systems could yield operational cost savings at locations where the natural gas (or other input fuel to the FC) price is much lower than the electricity price, such as in Ottawa. At locations where with exceptionally high natural gas to electricity price ratio, such as in Korea, no operational cost saving could be attained by the GSHP–FC system. The cost analysis results indicate that, in Ottawa, the extra capital investment incurred to the GSHP–FC system is possible to be returned within its lifespan, especially with the current trend of continuous price reductions of FC equipment and installation resulting from economy of scale and market expansion. Nevertheless, the GSHP–FC microgeneration systems' capability to generate both electricity and thermal energy at the point of use is generally considered more attractive for inclusion in the “smart” energy networks, new and remote community applications.

Microgeneration systems able to produce both heat and power at the point of use are beginning to emerge as a viable alternative to the large and expensive central power generating stations. Recently, the frequent blackouts around the world [1] have increased public awareness and interest in on-site small size generation (1–30 kWe) mainly due to the high efficiency performance, good environmental footprint and suitability to serve as both primary and back-up power generation [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26] and [27]. These systems are becoming even more attractive for new and remote community applications where costly construction of central generation stations and connection to the grid is neither affordable nor a preferable option [28] and [29]. Microgeneration systems are in size of 1–30 kWe and less than 50 kWth and are designed to satisfy all or part of the power/heating demands of a typical building or a group of buildings. Most of microgeneration systems can be integrated in smart energy networks and applied for both on-grid and off-grid applications. The systems are designed to recover the heat produced during the electricity generation process with consequent use for space and water heating in winter and in some cases thermal cooling in summer. Although microgeneration is an exciting emerging technology, it faces many challenges, for example in gaining market share in mature and competitive markets for domestic and commercial boilers, in further improving devices' efficiency and reducing cost, in increasing the operational life-time to recover the initial investment, and also in obtaining understanding of the technology both by installers and potential end users. Among these microgeneration research [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26] and [27], some [10], [11], [12], [13], [14], [15], [16], [24], [25], [26] and [27] have studied hybrid microgeneration system with integration of renewable energies. Fuel cell (FC) based microgeneration systems gained a wide range of interests due to their potential to operate with higher electrical efficiency. However, among many FC microgeneration researches [17], [18], [19], [20], [21], [22], [23], [24], [25], [26] and [27], most were focused on one technology or comparison of different technologies. Only few have studied hybrid systems with integration of FC and geothermal source [24], [25], [26] and [27]. Currently, Annex 54 of the International Energy Agency's Energy in Buildings and Communities Programme (IEA/EBC) is undertaking an in-depth analysis of microgeneration and associated other energy technologies [30]. The Annex 54 includes, among many research activities, study of multi-source micro-cogeneration systems, polygeneration systems and renewable hybrid systems, and analysis of integrated and hybrid systems performance when serving single and multiple residences along with small commercial premises [30]. To fulfill part of the IEA/EBC Annex 54's objectives, Entchev et al. [31] investigated the performance of an integrated ground sources heat pump (GSHP) and natural gas fueled fuel cell microgeneration system in load sharing application between a detached house and a small office building. The study shows that the GSHP–FC microgeneration system achieved a significant overall energy saving compared to a conventional system that utilizes boiler and chiller to meet the thermal and electric loads of the two buildings. However, in order to thoroughly evaluate the system performance, both energy and cost savings should be considered. To continue the previous work performed by Entchev et al. [31], this study investigates the performance of GSHP–FC microgeneration systems that serving multiple residential and small office buildings (instead of one house and one small office as studied in Ref. [31]) to approach real-life small neighborhood situations. In addition to the energy analyses, the cost analyses are conducted in order to thoroughly evaluate the performance of each studied system. The energy and cost performance of four GSHP–FC systems (with various FC capacities) are compared to a GSHP only system. It is expected that whether a GSHP–FC microgeneration system is economically feasible compared to a GSHP system is strongly dependent on the local natural gas and electricity prices and also on the building heating, cooling and electrical loads and their patterns. Therefore, the impact of the geographic location, FC capacity, utility prices (natural gas and electricity prices) and their billing structures on the system's energy and cost performance is examined in this study. It should be noted that there are considerable amount of interests in the optimization of distributed energy resources. The cost optimization of a network of micro combined heat and power systems at the neighborhood level is examined by Kopanos et al. [32] and the annualized overall investment and operating cost of a variety of competing microgeneration technologies is minimized [28]. However, the present study focuses on the energy and cost analyses of a centralized GSHP–FC system. The optimization of the investigated hybrid microgeneration systems and the inclusion of multiple distributed microgeneration resources within a microgrid will be considered in the future study.

This study investigated the energy and cost performance of hybrid GSHP–FC microgeneration systems serving multiple residential and small office buildings in Ottawa (Canada) and Incheon (South Korea). The results from the energy analysis show that the GSHP–FC systems have much higher annual natural gas consumption in order for electricity generation, but require less electricity from the grid compared to the GSHP only system. Overall, the GSHP–FC systems have less primary energy consumption in both locations in comparison to the GSHP system. The primary energy consumption of the GSHP–FC system decreases with the increase of the FC capacity. The cost analysis reveals that, in comparison to the GSHP only system, the GSHP–FC system had lower operational cost in Ottawa where the natural gas price is much lower than the electricity price. The saving increases with the increase of the FC capacity due to the fact that less electricity was required from the grid. The cost analysis also confirms that whether a GSHP–FC system could achieve operational cost saving is strongly dependent on the local natural gas and electricity prices and also on the building heating, cooling and electrical demands and their load profiles. The comparison of annual operational cost saving at various utility prices demonstrates that in order for the hybrid GSHP–FC system to achieve operational cost saving compared to the GSHP system, the natural gas price ($/m3) to the electricity price ($/kWh) ratio has to be less than 4.80 for the system with 7 kWe FC capacity and 4.96 for the system with 13 kWe FC capacity. The systems in Incheon did not yield operational cost savings because of exceptionally high natural gas to electricity price ratio (11.4) in Korea compared to that of in Canada (where ratio is 1.6). The cumulative discounted saving of the GSHP–FC systems in Ottawa indicates that the extra capital costs incurred to the GSHP–FC systems compared to the GSHP system could be fully recovered over their lifespan with continuing price reductions on equipment and installation resulting from economy of scale and market expansion. The cost analysis results also suggest that it is better to size the FC unit at least to cover the average electric load instead of the base load to gain maximum return. In summary, the GSHP–FC system has less primary energy consumption compared to the GSHP only system. It could be economically feasible at locations where the natural gas (or other input fuel) price is much lower than the electricity price. In addition, its capability to generate both electricity and thermal energy at the point of use is considered more attractive for inclusion in the “smart” energy networks and new and remote community applications.