| 1. |
- Adom, Philip Kofi
(författare)
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Business cycle and economic-wide energy intensity: The implications for energy conservation policy in Algeria
- 2015
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 88, s. 334-350
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Tidskriftsartikel (refereegranskat)abstract
- Despite the prevalence of voluntary and involuntary energy conservation policies, developing countries in Africa continue to struggle to achieve energy efficiency targets. Consequently, energy intensity levels have risen threatening the security of the energy system. This raises the important question: is there an economic state that induces agents to be energy conscious? In this study, we study the case of Algeria's energy intensity from 1971 to 2010. First, the paper argues that there is a certain economic state that economic agents find investing in energy conservation a viable option. Any state different from that would mean not investing in energy conservation. Second, the paper argues that the economy can do better even with an infinitesimal reduction in fuel subsidy, and that the gains in revenue from the policy can compensate for the negative socio-economic and equity impacts associated with such a policy. Third, the paper argues that, so long as, industrial expansion in the country move parallel with investment in technological innovation, long-term sustainable growth and energy conservation targets are jointly feasible. Fourth, the paper shows that income elasticity evolves with the business cycle, and the absorptive capability of the host country affects how FDI (foreign direct inflows) impact energy intensity. (C) 2015 Elsevier Ltd. All rights reserved.
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| 2. |
- Adom, Philip Kofi
(författare)
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Determinants of energy intensity in South Africa: Testing for structural effects in parameters
- 2015
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 89, s. 334-346
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Tidskriftsartikel (refereegranskat)abstract
- A cursory look at South Africa's energy data reveals that, energy intensity has consistently declined for the past two decades. The logical question that ensues is; what might have contributed to this phenomenon? The current study aims to investigate how different phenomena have contributed to the decline in South Africa's energy intensity. The study also tests for structural effects in the model parameters. The result showed that the de-industrialisation since 1980 and the changes in trade structure in favour of more imports have contributed significantly to the decline in energy intensity, in South Africa. Also, the current industry composition has induced technological transfer via FDI (Foreign direct inflows) and this has contributed to the decline in energy intensity levels, in South Africa. The individual effect analyses showed that each of the predictors shared significant amount of variance with the regression effect. Finally, there are significant structural effects in the parameters, and this has rendered the effects of regressors asymmetric. (C) 2015 Elsevier Ltd. All rights reserved.
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| 3. |
- Aichmayer, Lukas, et al.
(författare)
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Experimental evaluation of a novel solar receiver for a micro gas-turbine based solar dish system in the KTH high-flux solar simulator
- 2018
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 159, s. 184-195
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found.
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| 4. |
- Anglart, Henryk, 1954-, et al.
(författare)
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Mechanistic modelling of dryout and post-dryout heat transfer
- 2018
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 161, s. 352-360
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a new mechanistic model for the diabatic annular two-phase flow is presented and applied to prediction of dryout and post-dryout heat transfer in various channels. The model employs a computational fluid dynamics code - OpenFOAM (R) - to solve the governing equations of two-phase mixture flowing in a heated channel. Additional closure laws have been implemented to calculate the location of the dryout and to predict wall temperature in the post-dryout region. Calculated results have been compared with experimental data obtained in pipes and good agreement between predictions and measurements has been achieved. The presented model is applicable to complex geometries and thus can be used for prediction of post-dryout heat transfer in a wide variety of energy conversion systems.
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| 5. |
- Anjo, J., et al.
(författare)
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Modeling the long-term impact of demand response in energy planning : The Portuguese electric system case study
- 2018
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 165, s. 456-468
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Tidskriftsartikel (refereegranskat)abstract
- With the urge to decrease carbon emissions, electricity systems need to evolve to promote the integration of renewable resources and end-use energy efficiency. Demand Response (DR) can be used as a strategy, one among many, to improve the balance between demand and supply of electricity, especially in systems that rely heavily on variable energy renewable resources. Thus, it is important to understand up to what extent a countrywide system would cope with DR implementation. In this work, the impact of demand response in the long-term is assessed, using a model of the Portuguese electricity system in the modeling tool OSeMOSYS. The theoretical potential of DR is computed to understand better the impact on the overall system planning, by analyzing three scenarios – a business as usual scenario, a carbon-free system scenario in 2050, and a scenario without heavy carbon emission restrictions. DR impact in all three scenarios results in a decrease in the overall costs, on the capacity installed and in an increase in the percentage of renewable capacity. Further, an economic analysis showed that DR would take 15 years, on average, to influence the average electricity cost and that the reduction in total costs is mainly due to the avoided capacity investments.
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| 6. |
- Arnaudo, Monica, et al.
(författare)
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Heat demand peak shaving in urban integrated energy systems by demand side management - A techno-economic and environmental approach
- 2019
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 186
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Tidskriftsartikel (refereegranskat)abstract
- The integration of variable renewable resources and decentralized energy technologies generates the need for a larger flexibility of the energy demand. In order to fully deploy a demand side management approach, synergies between interconnected energy systems have to be systematically implemented. By taking this standpoint, this study proposes a new approach to explore the potential of multi-energy integrated energy systems. This approach is constituted by two main steps, which are (1) the performance simulation of selected energy infrastructures and (2) the estimation of related techno-economic performance indicators. Step (1) expands the work presented in previous literature, by including a novel co-simulation feature. In step (2), the levelized cost of energy and location-dependent emission factors are used as key performance indicators. In this paper, the presented approach is demonstrated by implementing two demand side management options for heat peak demand shaving. A Swedish residential neighborhood is considered as a case study. The first option explores the potential of storing heat in the thermal mass of residential buildings. The proposed strategies lead to a decrease of up to 70% of primary energy consumption, depending on the indoor comfort requirements. The second option estimates the techno-economic feasibility of a new set of scenarios based on the integration of geothermal distributed heat pumps within a district heating network. The district heating scenario is found to be the most techno-economical convenient. Nevertheless, a moderate penetration of distributed heat pumps (around 20%) is shown to have a good trade-off with the reduction of CO2 emissions.
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| 7. |
- Averfalk, Helge, 1988-, et al.
(författare)
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Novel low temperature heat distribution technology
- 2018
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Ingår i: Energy. - London : Elsevier. - 0360-5442 .- 1873-6785. ; 145, s. 526-539
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Tidskriftsartikel (refereegranskat)abstract
- Lower future heat demands and lower availability of non-fossil high temperature heat supply are expected future market conditions that restrain the long-term viability of contemporary district heating systems. Hence, current district heating technology should be enhanced to increase system performance in new heat distribution areas. This paper aims to outline a proposal for technical improvements required to achieve lower annual average return temperatures in new residential buildings to improve viability in future market conditions. The proposed technical solution consists of three principle changes: three-pipe distribution networks, apartment substations, and longer thermal lengths for heat exchangers. The three technical modifications aims at addressing system embedded temperature errors. Furthermore, a simulation model was developed to assess the proposed technical solution concerning different energy performances of buildings and different thermal lengths in heat exchangers. The results show that implementation of the three technical modifications reaches time-weighted annual average return temperatures of 17–21 °C with supply temperatures of about 50 °C. The results also verify the increased necessity to separate the network return flows into delivery and recirculation flows in residential substations as energy performance in buildings increase.
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| 8. |
- Ayele, Getnet Tadesse, et al.
(författare)
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Optimal placement and sizing of heat pumps and heat only boilers in a coupled electricity and heating networks
- 2019
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Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 182, s. 122-134
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Tidskriftsartikel (refereegranskat)abstract
- Multi-energy systems are reported to have a better environmental and economic performance relative to the conventional, single-carrier, energy systems. Electrification of district heating networks using heat pumps and combined heat and power technologies is one such example. Due to lack of suitable modelling tools, however, the sizing and optimal placement of heat pumps is always done only from the heating network point of view which sometimes compromises the electricity network. This paper proposes an integrated optimization algorithm to overcome such limitation. A load flow model based on an extended energy hub approach is combined with a nested particle swarm optimization algorithm. A waste to energy combined heat and power plant, heat pumps (HPs), heat only boiler (HOB), solar photovoltaic, wind turbines and imports from the neighborhood grids are considered in the case studies. The results show that optimal placement and sizing of HPs and a HOB using the proposed methodology avoids an unacceptable voltage profiles and overloading of the electricity distribution network, which could arise while optimizing only from the heating network point of view. It also shows that up to 41.2% of the electric loss and 5% of the overall operating cost could be saved.
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| 9. |
- Baigmohammadi, Mohammadreza, et al.
(författare)
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Experimental study on the effects of mixture flow rate, equivalence ratio, oxygen enhancement, and geometrical parameters on propane air premixed flame dynamics in non-adiabatic meso-scale reactors
- 2017
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 121, s. 657-675
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the effects of reactive mixture flow rate, adding oxygen to propane-air mixture, geometrical parameters, and equivalence ratio on propane-air/oxygen premixed flame dynamics in non adiabatic meso-scale reactors were experimentally investigated. During the experiments, seven flame regimes of blow-off, blow-out, asymmetric stationary, stationary-repetitive extinction and re-ignition (RERI), forced/self-RERI, RERI-flash-back, and flash-back were observed. The results showed that increasing the reactive mixture flow rate could generally promote variety of the flame regimes and also improve flame stability in the non-adiabatic meso-scale reactors, especially in 40% and 80% oxygen enhanced cases. Also, the results demonstrated that increasing the reactor inner diameter and equivalence ratio generally extended propane-air- oxygen flame stability and its presence range in the non adiabatic meso-scale reactors. Moreover, it was shown that increasing the reactor length and also increasing the added oxygen to propane-air mixture more than 40% promoted flame instability and consequently restricted propane-air-oxygen flame presence range in the non-adiabatic meso-scale reactors. Also, it was shown that variations in the mixture flow rate, the reactor length and inner diameter, equivalence ratio, and oxygen concentration in propane-air mixture could significantly influence the flame average propagation speed, acoustic, and chemiluminescence in the non-adiabatic meso-scale reactors.
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| 10. |
- Bauer, N., et al.
(författare)
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Assessing global fossil fuel availability in a scenario framework
- 2016
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 111, s. 580-592
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses global, long-term economic availability of coal, oil and gas within the Shared Socio-economic Pathway (SSP) scenario framework considering alternative assumptions as to highly uncertain future developments of technology, policy and the economy. Diverse sets of trajectories are formulated varying the challenges to mitigation and adaptation of climate change. The potential CO2 emissions from fossil fuels make it a crucial element subject to deep uncertainties. The analysis is based on a well-established dataset of cost-quantity combinations that assumes favorable techno-economic developments, but ignores additional constraints on the extraction sector. This study significantly extends the analysis by specifying alternative assumptions for the fossil fuel sector consistent with the SSP scenario families and applying these filters (mark-ups and scaling factors) to the original dataset, thus resulting in alternative cumulative fossil fuel availability curves. In a Middle-of-the-Road scenario, low cost fossil fuels embody carbon consistent with a RCP6.0 emission profile, if all the CO2 were emitted freely during the 21st century. In scenarios with high challenges to mitigation, the assumed embodied carbon in low-cost fossil fuels can trigger a RCP8.5 scenario; low mitigation challenges scenarios are still consistent with a RCP4.5 scenario.
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