| 1. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Assessing the techno-economic impact of low-temperature subnets in conventional district heating networks
- 2017
-
Ingår i: Energy Procedia. - : Elsevier. - 1876-6102. ; 116:C, s. 260-272
-
Tidskriftsartikel (refereegranskat)abstract
- The 4th generation Low-Temperature District Heating (LTDH) is envisioned as a more efficient and environmentally friendly solution to provide heating services to the building stock. Specifically, in countries already with a large share of well-established DH systems, conventional DH and LTDH technologies will be operating simultaneously in the near future. Newly built or refurbished buildings have lower heat demands, which in combination with LTDH brings potential savings compared to conventional DH. This work explores the advantages in DH operation by connecting these loads via LTDH subnets to a conventional DH system, supplied by a Combined Heat and Power (CHP) plant. A techno-economic analysis was performed, through modelling and simulation, by estimating the annual DH operating costs and revenues achieved by the reduction in return temperatures that LTDH would bring. The savings are related to: (1) the reduction in distribution heat losses in the return pipe; and (2) lower pumping power demand. Likewise, additional revenues are assessed from: (3) improved Power-to-Heat ratio for electricity production; and (4) enhanced heat recovery through Flue Gas Condensation (FGC). The annual savings per kWh of delivered heat are estimated as a function of the penetration percentage of ‘energy efficient’ loads over the conventional DH network. Key outcomes show the trade-offs between the potential savings in operating costs and the reduction in heat demand: relative losses in this scenario are maintained at 13.1% compared to 15.3% expected with conventional DH; and relative pumping power demand decreased as well. In other words, the costs of supplying heat decrease, even though the total heat supplied is reduced.
|
|
| 2. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Conceptual study of a solar-assisted low-temperature district heating substation
- 2015
-
Ingår i: Book of abstracts: International Conference on Smart EnergySystems and 4th Generation District Heating. - Copenhagen, DK : Aalborg Universitetsforlag.
-
Konferensbidrag (refereegranskat)abstract
- At present, the viability of Low-Temperature District Heating (LTDH) systems has already been tested and demonstrated. Even so, for LTDH to be successfully implemented, further ideas are needed in order to improve the flexibility and effectiveness. In this study, we analyze the performance of a local LTDH network for a multi-dwelling low-energy building supplied by both a roof-mounted solar collector and the conventional DH network via a LTDH substation. The DH network serves as a short-term storage buffer, so no heat storages are required. The collector’s size is chosen based on the available roof area, independently from the building’s loads, and three possible connection configurations were simulated. A mix of both the existing DH forward and return flows are used as thermal energy sources. The results show that more than 15% of the summer heat demand in the LTDH network can be covered by the roof-mounted solar collector. With a feed-in contract, heat costs savings range 3-6% annually according to the Swedish system. System integration in LTDH from the design phase has the potential to enhance the recovery of solar thermal energy, increase its conversion efficiency, and in general, to improve the utilization of low-grade thermal energy sources.
|
|
| 3. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Energetic and exergetic analysis of a low- Temperature based district heating substation for low energy buildings
- 2015
-
Ingår i: ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
-
Konferensbidrag (refereegranskat)abstract
- District Heating (DH) technology contributes to the low GHG emissions energy system, facilitates a renewable energy usage, and increases the overall system efficiency, while providing the necessary heating services to the built environment. However, the existing DH technology may not be technically and economically effective to service buildings with low-energy demands. Here, low- Temperature based district heating (LTDH) provides a better match between supply and demand in terms of energy quality. This paper deals with the energy and exergy analyses of a LTDH substation supplying a secondary LTDH network as a subnet of the existing DH system. The substation is supplied with a mix of supply and return flows from the main DH network. An energy and exergy analysis was employed based on modelling and simulation to compare the performance of two proposed substation configurations to that of a conventional DH substation operating at low- Temperature. The study was performed for a year round outdoor temperatures scenario under steady-state conditions. The exergy destruction at the system components was identified and compared. The results of this analysis show that by using the low- Temperature flow from the DH return pipe, the final exergy efficiency of the overall system is increased. On the other hand, assuming an adiabatic system the energy performance stays the same. As compared with the conventional DH network, the integration of the proposed LTDH substation reduced the share of energy demand covered by the main DH supply by 20-25% and improved the overall exergy efficiency from 79% to 85-87% depending on the substation configuration. Based on the results, the solution presented is seen as an effective approach to reduce the system's losses, and to increase the quality match between the low-energy heating demands and the supply.
|
|
| 4. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Energetic and exergetic analysis of alternative low-temperature based district heating substation arrangements
- 2016
-
Ingår i: International Journal of Thermodynamics. - : International Centre for Applied Thermodynamics (ICAT). - 1301-9724 .- 2146-1511. ; 19:2, s. 71-80
-
Tidskriftsartikel (refereegranskat)abstract
- District Heating (DH) technology is an efficient and cost-effective solution to provide heating services to the built environment. However, the existing DH technology may not be technically and economically effective to service buildings with low energy demands. Here, low-temperature based district heating (LTDH) can provide a better match between supply and demand in terms of energy quality and quantity. This paper deals with the energy and exergy analyses of a LTDH substation supplying a secondary LTDH network as a subnet of the existing DH system. In order to improve the temperature match, a mix of supply and return streams from the main DH network are used to supply the substation. Based on modelling and simulation, an energy and exergy analysis is employed to compare the performance of two proposed substation configurations to that of a conventional DH substation operating at low temperatures. The results of this analysis show that the proposed LTDH substation reduced the share of energy demand covered by the main DH supply by 20% to 25%. Likewise, by using the flow from the main DH return pipe, the final exergy efficiency of the overall system increased by 5% on average. The exergy destruction occurring at the system components was also identified and compared: during high heat demands the substation heat exchanger is responsible for the largest share of exergy destruction, whereas for low heat demands, it is due to the pumping effort. Based on these results, the proposed system is seen as an effective approach to increase the quality and quantity match between the low-temperature network and the conventional supply.
|
|
| 5. |
- Castro Flores, José Fiacro
(författare)
-
Low-temperature based thermal micro-grids: operation and performance assessments
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energy use in the urban environment is vital for the proper functioning of our society, and in particular, comfort heating –or cooling– is a central element of our energy system often taken for granted. Within this context, district energy systems and especially, district heating (DH) systems must evolve to adapt to the upcoming decades-long transition towards a sustainable energy system. This dissertation seeks to introduce, discuss, and assess from a techno-economic perspective the concept of low-temperature (LT) based thermal micro-grids (subnets) as active distribution thermal networks. It explores the role of the subnet at the system distribution level supervised by an active agent (DH substation), performing tasks of heat supply and demand management (storage and dispatch), as well as coordinating bidirectional flows. Here, a mixed methodological approach based on analytical simulation for the assessment of alternatives to evaluate a set of technologies is developed and discussed. This approach covers: the identification of knowledge gaps through the state-of-the-art analysis; a collection of incremental technical and/or economic performance assessments; and the analysis of a measurement data set from an existing LTDH demonstration project. Key findings of this work include: an updated and improved model of aggregated heat loads; identification of differences in load and temperature patterns for certain LT subnets; analysis of benefits and drawbacks of active substations with distributed heat sources and/or storage; and the impact on the reduction of the primary network return temperature as a consequence of the increase in the share of LT subnets, leading to lower generation and operating costs. These outcomes reveal that the integrated design and operation of the active thermal micro-grid have the potential to improve both the performance of the subnet, and that of the primary network. It further enhances the capability of the overall system to integrate unconventional and distributed heat sources together with energy efficient buildings by increasing the system’s flexibility and controllability. Active thermal distribution networks will likely become a subsequent step in the technological development of DH technologies, to address the matter of providing comfort heating in an effective and cost-efficient manner. This work advances the current DH knowledge by identifying synergies and challenges that arise with these new developments, in order for DH technology to play a key role in the future smart and sustainable energy system.
|
|
| 6. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Study of a district heating substation using the return water of the main system to service a low-temperature secondary network
- 2014
-
Ingår i: Proceedings of The 14th International Symposium on District Heating and Cooling. - Stockholm, SE : Swedish District Heating Association. - 9789185775248
-
Konferensbidrag (refereegranskat)abstract
- The development of district heating (DH) systems is facing the challenge of servicing areas with lower energy demands whose connection might not be either effective or profitable if the conventional DH technology is used. The purpose of this paper is to propose a complementary approach on how to effectively service low-energy building (LEB) areas using the existing DH networks. The proposed solution consists in supplying a secondary low-temperature (LT) network by means of a ‘low temperature’ substation that uses the return water from the main DH network as a substitute for the primary energy source, together with a minor portion of the main DH supply. Two types of LT substations are proposed and compared to a reference substation: First, a one-stage heat exchanger that uses a mixture of the main DH network return and supply flows as thermal energy source. Second, a two-stage heat exchanger that is fed by both the main DH return and supply flows. The system subject to this study consists on the LT substation with supply/return temperatures at 55/25 °C average. The system energetic performance is analysed though thermodynamic simulation. Outdoor ambient temperatures variations throughout the year are considered for two specific locations, assuming full and partial load operation. The results show that it is possible to supply 20-50% of the total annual heat demand of a LTDH network using the return flow from the main DH network. The solution presented in this paper is seen as being of potential interest to deliver thermal energy services to LEB areas.
|
|
| 7. |
- Castro Flores, José Fiacro, et al.
(författare)
-
Techno-Economic Assessment of Active Latent Heat Thermal Energy Storage Systems with Low-Temperature District Heating
- 2017
-
Ingår i: International Journal of Sustainable Energy Planning and Management. - 2246-2929. ; , s. 5-17
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal energy storage (TES) is a set of technologies with the potential to enhance the efficiency and flexibility of the 4th generation of district heating systems. This study presents a comparative techno-economic assessment of active TES systems suited to operate with low-temperature district heating (LTDH) for short-term heat storage applications. Latent heat systems (LH-TES) are compared qualitatively and quantitatively to water-based sensible heat systems (SH-TES). It is concluded that latent heat TES systems are still more expensive than water-based systems regarding energy storage cost (EUR/kWh) ranging from 1.5 to 4 times more, mainly due to the cost of the storage media. However, considering distributed TES systems integrated to LTDH, small-scale active LH-TES systems will become more cost-competitive as storage media costs are expected to decline in the future. This study represents a step forward in the development and improvement of the DH system through the integration of TES which will play a key role in the future smart energy system.
|
|
| 8. |
- Chiu, Justin N. W., et al.
(författare)
-
Industrial surplus heat transportation for use in district heating
- 2016
-
Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 110, s. 139-147
-
Tidskriftsartikel (refereegranskat)abstract
- M-TES (Mobile Thermal Energy Storage) technology is explored in this paper for transportation of industrial surplus heat for use in LTDH (low temperature district heating network). LTDH has promising potential in utilizing low grade heat, on the other hand, 20%–50% of industry generated surplus heat is often released to the ambient environment. M-TES is used to match thermal energy supply and demand that occur at different locations and that are shifted in time. In this paper, design of M-TES is conducted, optimization in operating strategies is performed, sensitivity analysis on levelized cost is studied, and environmental impact of CO2 emissions due to transportation is evaluated. The results of the study show an array of transportation means and storage operating strategies under which M-TES is technically, economically and environmentally sound for transportation of industrial surplus heat for use in LTDH network.
|
|
| 9. |
- Chiu, NingWei Justin, et al.
(författare)
-
Environomic Assessment of Industrial Surplus Heat Transportation
- 2015
-
Ingår i: Smart Energy Infrastructure and Storage Options.
-
Konferensbidrag (refereegranskat)abstract
- The fourth generation low temperature district heating network (LTDH) has to meet challenges in supplying low temperature heat, achieving low grid losses, integrating renewable heat sources, assimilating smart energy system and ensuring suitable planning structure. The new generation LTDH has promising potential in utilizing low grade waste heat where heat at temperature of as low as 55°C can be injected into the system. Industry generated surplus heat is often released to the ambient environment due to their remote location from end users. A solution is presented here to exploit the potential of recycling low grade industrial surplus heat for use in LTDH network.Mobile Thermal Energy Storage (M-TES) is used for shifting thermal energy to meet supply and demands that occur in different locations and that are shifted in time. M-TES technology is explored in this paper for utilization of industrial surplus heat in LTDH. Technical feasibility has been previously established with finned pipe and tube & shell type heat exchangers, however the economic justification is not always demonstrated. In this paper, parametric study on operating conditions, operating strategies and component costs will be performed. Furthermore, environmental impact from CO2 emissions due to different transportation means production will be evaluated against other heat production possibilities, such as conventional natural gas boilers. The results of the study show the optimal transportation distance, transportation means, partial/full storage operating conditions, storage means and power to energy ratio (PER) under which M-TES are technically, economically and environmentally sound for transportation of industrial surplus heat for use in the 4th generation LTDH network.
|
|
| 10. |
- Rossi Espagnet, Alberto, et al.
(författare)
-
Techno-economic assessment of Thermal Energy Storage integration into Low Temperature District Heating networks
- 2016
-
Ingår i: Book of abstracts. - : Aalborg Universitetsforlag.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Thermal energy storage (TES) systems are technologies with the potential to enhance the efficiency and the flexibility of the coming 4th generation low temperature district heating (LTDH). Their integration would enable the creation of smarter, more efficient networks, benefiting both the utility and the end consumers. This study aims to develop a comparative assessment of TES systems, both latent and sensible heat based. First, a techno-economic analysis of several TES systems is conducted to evaluate their suitability to be integrated into LTDH. Then, potential scenarios of TES integration are analysed in a case study of a LTDH network. This is complemented with a review of current DH legislation focused on the Swedish case, with the aim of taking into consideration the present situation, and changes that may support some technologies over others. The results of the analysis show that sensible heat storage is still preferred to latent heat when coupled with LTDH: the cost per kWh stored is still 15% higher for latent heat in systems below 5MWh of storage size; though, they require just half of the volume. However, it is expected that the cost of latent heat storage systems will decline in the future, making them more competitive. From a system perspective, the introduction of TES systems into the network results in an increase in flexibility leading to lower heat production costs by load shifting: by running the production units with lower marginal heat production costs for longer periods and with high efficiency, and thus reducing the operating hours of the other more expensive operating units during peak load conditions. These results may also be extended to the case when heat generation is replaced by renewable, intermittent energy sources; thus increasing profits, reducing fuel consumption, and consequently emissions. This study represents a step forward in the development of a more efficient DH system through the integration of TES which will play a crucial role in future smart energy system.
|
|
