7,551 research outputs found
A novel bidding method for combined heat and power units in district heating systems
We propose a bidding method for the participation of combined heat and power
(CHP) units in the day-ahead electricity market. More specifically, we consider
a district heating system where heat can be produced by CHP units or heat-only
units, e.g., gas or wood chip boilers. We use a mixed-integer linear program to
determine the optimal operation of the portfolio of production units and
storages on a daily basis. Based on the optimal production of subsets of units,
we can derive the bidding prices and amounts of electricity offered by the CHP
units for the day-ahead market. The novelty about our approach is that the
prices are derived by iteratively replacing the production of heat-only units
through CHP production. This results in an algorithm with a robust bidding
strategy that does not increase the system costs even if the bids are not won.
We analyze our method on a small realistic test case to illustrate our method
and compare it with other bidding strategies from literature, which consider
CHP units individually. The analysis shows that considering a portfolio of
units in a district heating system and determining bids based on replacement of
heat production of other units leads to better results
Modeling Time-dependent CO Intensities in Multi-modal Energy Systems with Storage
CO emission reduction and increasing volatile renewable energy generation
mandate stronger energy sector coupling and the use of energy storage. In such
multi-modal energy systems, it is challenging to determine the effect of an
individual player's consumption pattern onto overall CO emissions. This,
however, is often important to evaluate the suitability of local CO
reduction measures. Due to renewables' volatility, the traditional approach of
using annual average CO intensities per energy form is no longer accurate,
but the time of consumption should be considered. Moreover, CO intensities
are highly coupled over time and different energy forms due to sector coupling
and energy storage. We introduce and compare two novel methods for computing
time-dependent CO intensities, that address different objectives: the first
method determines CO intensities of the energy system as is. The second
method analyzes how overall CO emissions would change in response to
infinitesimal demand changes. Given a digital twin of the energy system in form
of a linear program, we show how to compute these sensitivities very
efficiently. We present the results of both methods for two simulated test
energy systems and discuss their different implications.Comment: This work has been submitted to the Elsevier Applied Energy for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
Short-term Self-Scheduling of Virtual Energy Hub Plant within Thermal Energy Market
Multicarrier energy systems create new challenges as well as opportunities in future energy systems. One of these challenges is the interaction among multiple energy systems and energy hubs in different energy markets. By the advent of the local thermal energy market in many countries, energy hubs' scheduling becomes more prominent. In this article, a new approach to energy hubs' scheduling is offered, called virtual energy hub (VEH). The proposed concept of the energy hub, which is named as the VEH in this article, is referred to as an architecture based on the energy hub concept beside the proposed self-scheduling approach. The VEH is operated based on the different energy carriers and facilities as well as maximizes its revenue by participating in the various local energy markets. The proposed VEH optimizes its revenue from participating in the electrical and thermal energy markets and by examining both local markets. Participation of a player in the energy markets by using the integrated point of view can be reached to a higher benefit and optimal operation of the facilities in comparison with independent energy systems. In a competitive energy market, a VEH optimizes its self-scheduling problem in order to maximize its benefit considering uncertainties related to renewable resources. To handle the problem under uncertainty, a nonprobabilistic information gap method is implemented in this study. The proposed model enables the VEH to pursue two different strategies concerning uncertainties, namely risk-averse strategy and risk-seeker strategy. For effective participation of the renewable-based VEH plant in the local energy market, a compressed air energy storage unit is used as a solution for the volatility of the wind power generation. Finally, the proposed model is applied to a test case, and the numerical results validate the proposed approach
Analysis of the economic feasibility and reduction of a building’s energy consumption and emissions when integrating hybrid solar thermal/PV/micro-CHP systems
The aim of this paper is to assess the performance of several designs of hybrid systems composed of solar thermal collectors, photovoltaic panels and natural gas internal combustion engines. The software TRNSYS 17 has been used to perform all the calculations and data processing, as well as an optimisation of the tank volumes through an add-in coupled with the GENOPT® software. The study is carried out by analysing the behaviour of the designed systems and the conventional case in five different locations of Spain with diverse climatic characteristics, evaluating the same building in all cases. Regulators, manufacturers and energy service engineers are the most interested in these results.
Two major contributions in this paper are the calculations of primary energy consumption and emissions and the inclusion of a Life Cycle Cost analysis. A table which shows the order of preference regarding those criteria for each considered case study is also included. This was fulfilled in the interest of comparing between the different configurations and climatic zones so as to obtain conclusions on each of them. The study also illustrates a sensibility analysis regarding energy prices. Finally, the exhaustive literature review, the novel electricity consumption profile of the building and the illustration of the influence of the cogeneration engine working hours are also valuable outputs of this paper, developed in order to address the knowledge gap and the ongoing challenges in the field of distributed generation
Operational planning and bidding for district heating systems with uncertain renewable energy production
In countries with an extended use of district heating (DH), the integrated
operation of DH and power systems can increase the flexibility of the power
system achieving a higher integration of renewable energy sources (RES). DH
operators can not only provide flexibility to the power system by acting on the
electricity market, but also profit from the situation to lower the overall
system cost. However, the operational planning and bidding includes several
uncertain components at the time of planning: electricity prices as well as
heat and power production from RES. In this publication, we propose a planning
method that supports DH operators by scheduling the production and creating
bids for the day-ahead and balancing electricity markets. The method is based
on stochastic programming and extends bidding strategies for virtual power
plants to the DH application. The uncertain factors are considered explicitly
through scenario generation. We apply our solution approach to a real case
study in Denmark and perform an extensive analysis of the production and
trading behaviour of the DH system. The analysis provides insights on how DH
system can provide regulating power as well as the impact of uncertainties and
renewable sources on the planning. Furthermore, the case study shows the
benefit in terms of cost reductions from considering a portfolio of units and
both markets to adapt to RES production and market states
Locating a bioenergy facility using a hybrid optimization method
In this paper, the optimum location of a bioenergy generation facility for district energy applications is sought. A bioenergy facility usually belongs to a wider system, therefore a holistic approach is adopted to define the location that optimizes the system-wide operational and investment costs. A hybrid optimization method is employed to overcome the limitations posed by the complexity of the optimization problem. The efficiency of the hybrid method is compared to a stochastic (genetic algorithms) and an exact optimization method (Sequential Quadratic Programming). The results confirm that the hybrid optimization method proposed is the most efficient for the specific problem. (C) 2009 Elsevier B.V. All rights reserved
A new method to energy saving in a micro grid
Optimization of energy production systems is a relevant issue that must be
considered in order to follow the fossil fuels consumption reduction policies and CO2 emission
regulation. Increasing electricity production from renewable resources (e.g., photovoltaic
systems and wind farms) is desirable but its unpredictability is a cause of problems for the
main grid stability. A system with multiple energy sources represents an efficient solution,
by realizing an interface among renewable energy sources, energy storage systems, and
conventional power generators. Direct consequences of multi-energy systems are a wider
energy flexibility and benefits for the electric grid, the purpose of this paper is to propose
the best technology combination for electricity generation from a mix of renewable energy
resources to satisfy the electrical needs. The paper identifies the optimal off-grid option
and compares this with conventional grid extension, through the use of HOMER software.
The solution obtained shows that a hybrid combination of renewable energy generators at
an off-grid location can be a cost-effective alternative to grid extension and it is sustainable,
techno-economically viable, and environmentally sound. The results show how this innovative
energetic approach can provide a cost reduction in power supply and energy fees of 40%
and 25%, respectively, and CO2 emission decrease attained around 18%. Furthermore, the
multi-energy system taken as the case study has been optimized through the utilization of
three different type of energy storage (Pb-Ac batteries, flywheels, and micro—Compressed Air
Energy Storage (C.A.E.S.)
An optimization model for multi-biomass tri-generation energy supply
In this paper, a decision support system (DSS) for multi-biomass energy conversion applications is presented. The system in question aims at supporting an investor by thoroughly assessing an investment in locally existing multi-biomass exploitation for tri-generation applications (electricity, heating and cooling), in a given area. The approach followed combines use of holistic modelling of the system, including the multi-biomass supply chain, the energy conversion facility and the district heating and cooling network, with optimization of the major investment-related variables to maximize the financial yield of the investment. The consideration of multi-biomass supply chain presents significant potential for cost reduction, by allowing spreading of capital costs and reducing warehousing requirements, especially when seasonal biomass types are concerned. The investment variables concern the location of the bioenergy exploitation facility and its sizing, as well as the types of biomass to be procured, the respective quantities and the maximum collection distance for each type. A hybrid optimization method is employed to overcome the inherent limitations of every single method. The system is demand-driven, meaning that its primary aim is to fully satisfy the energy demand of the customers. Therefore, the model is a practical tool in the hands of an investor to assess and optimize in financial terms an investment aiming at covering real energy demand. optimization is performed taking into account various technical, regulatory, social and logical constraints. The model characteristics and advantages are highlighted through a case study applied to a municipality of Thessaly, Greece. (C) 2008 Elsevier Ltd. All rights reserved
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