•A novel grid-cell approach to estimate global solar energy potential.•Solar potentials constrained by land-use, technology conversion and net energy.•A new solar-to-electric efficiency ...parametrization for CSP power plants.•Power plants design optimised by maximising the Energy Return on Investment.•Solar potential is established between 1089 and 165 EJ/year at EROImin from 5 to 9.
The amount of energy striking the earth’s surface in one hour is higher than global annual societies energy use, yet the fraction of incoming solar radiation that can be harvested is significantly constrained. A global grid-cell methodology was adopted to assess the available global solar energy potential taking into account four constraints: land-use, solar irradiation, solar-to-electric technology, and net energy. Net energy is the amount of energy that is delivered to end-users, after subtraction of the energy inputs needed for capital infrastructure and operation. Both photovoltaic and concentrated solar power technologies are considered. The resulting constrained solar potential worldwide was estimated at 1098 exajoules per year, of which 98%, 75%, and only 15% can be extracted if the system needs to deliver an energy return on energy invested set at 5, 7.5, and 9, respectively. The resulting global solar potential is substantially lower than most previous estimates. Depending on how high the energy return needs to be relative to the energy investment needed to maintain a sustainable society, the achievable potential will be significantly constrained. The effect is especially significant in lower solar radiation regions. The European Union holds only 2% of the global solar net energy potential.
Despite a substantial literature using life cycle assessment (LCA) approach, the extent to which second and third generation biofuels are more sustainable than the first generation remains a subject ...of debate. Although the existence of limitations due to LCA variability and uncertainty, this paper intends to determine global tendencies based on a statistic and critical interpretation of previously published study results, reviewing 61 recent papers addressing an environmental evaluation of microalgae biofuels. Such information is compared to the same impact indicators for fossil fuels and for ethanol and biodiesel from terrestrial crops in Europe and Brazil. For each case, the system boundaries and the methodological choices were precisely described. The sustainability potential of all biofuels was evaluated by the Global Warming Potential (GWP), the Energy Ratio (ER) and the Land Use (LU), allowing a broad estimation of the biofuels’ contribution to climate change mitigation, their net energy efficiency and their competiveness with food production chain.
The results highlight that algae-derived biodiesel is, by far, the most efficient alternative in terms of land use compared to other biofuels, avoiding competition with food crops. Some biodiesel pathways can also satisfactorily perform in terms of greenhouse gases emissions reduction, but some others can be even worst than fossil diesel. Nevertheless, in terms of energy efficiency, algae biofuels cannot compete with other biofuels or fossil fuels. They present very low performances, even demanding more energy for its production then the energy they can deliver. Moreover, no pathway can be conclusively selected as preferable between the two main technologies available for microalgae biodiesel due to high uncertainties. However, open raceway pounds technology seems to be preferable as it looks less GHG intensive, requiring lower energy input and land use. Energetic and GWP performances can be improved if production pathways are carefully chosen and optimized.
Supply chains are dynamic and complex systems. This holds particularly true for humanitarian supply chains that operate under strong uncertainty. In view of an ever‐growing gap of unmet humanitarian ...needs, it is essential to gain a better understanding of the behavior of humanitarian supply chain systems. Despite a growing academic output in this field, there is a lack of empirical studies that take an integrated view on humanitarian supply chains and support decision makers with fact‐based evidence. Based on four extensive case studies and existing literature, we developed a system dynamics model that reflects the operational reality of humanitarian organizations in form of their centralized, hybrid and decentralized settings. The model provides a holistic supply chain view and measures the operational performance with regard to response cost, delivery lead time and impact on the local economy. Furthermore, we studied the impact of preparedness investments to enhance operational performance in the supply chain and deliver more humanitarian assistance with the limited resources available. Finally, we used our model to analyze the impact of major shocks such as the COVID‐19 pandemic to assess the vulnerability of humanitarian supply chains. The results indicate that operational settings, product and disaster characteristics have a major influence on the supply chain performance both in the noninvestment case as well as in the case where preparedness investments have been made. Specifically, for low‐value items, we find that decentralized settings have the lowest supply chain costs while for high‐value items the price difference between local and international procurement determines which setting is the most cost‐effective one. The preferability of the supply chain setting strongly depends on the indicator chosen. Hence, ultimately, the findings emphasize the need to apply appropriate indicators and identify their trade‐offs to comprehensively analyze the performance of humanitarian supply chain settings. The newly introduced Humanitarian Return‐on‐Investment concept can play an important role in this context.
•Effect of microwave power level was stronger than that of processing time.•The HHV of biochar was up to 30MJ/kg.•The fuel ratio of biochar was as high as 3.7.•The EROI of microwave torrefaction was ...34 when at a handling capacity of 200g.•Kinetic parameters were determined.
This study carried out leucaena torrefaction by using microwave heating to investigate the fuel properties of biochar and the energy efficiency of the technique. Both maximum temperature and heating rate increased with increasing microwave power level. Processing time was also an important operational parameter, but its effect was weaker than that of microwave power. The heating value of torrefied product was higher at higher power level and longer processing time, but the mass and energy yields were lower due to higher energy input and thus more intense reaction. Heating value was approximately 30MJ/kg at a microwave power level of 250W for 30min processing time. The fuel ratio of torrefied leucaena was up to 3.7, which is much higher than that of bituminous coal and thus can be regarded as an alternative fuel to replace coal or co-fire with it. The energy return on investment of microwave torrefaction of leucaena can be 1.4, 17, and 34 when the handling capacities are 8, 100, and 200g, respectively. Therefore, microwave torrefaction of leucaena is a promising technique that can be feasible if deployed at industrial scale. Activation energy and pre-exponential factor were 24.46kJ/mol and 9.661/s, respectively.
•A novel methodology to estimate global wind energy potential is proposed.•Wind park suitability is constrained by land use and water depth.•Power production density is derived from energy ...conservation laws.•Maximum wind potential is dependent on minimum Energy Return on Investment.•Total potential is established between 700 and 100EJ/year at EROImin from 5 to 12.
Looking ahead to 2050 many countries intend to utilise wind as a prominent energy source. Predicting a realistic maximum yield of onshore and offshore wind will play a key role in establishing what technology mix can be achieved, specifying investment needs and designing policy. Historically, studies of wind resources have however differed in their incorporation of physical limits, land availability and economic constraints, resulting in a wide range of harvesting potentials. To obtain a more reliable estimate, physical and economic limits must be taken into account.
We use a grid-cell approach to assess the theoretical wind potential in all geographic locations by considering technological and land-use constraints. An analysis is then performed where the Energy Return on Investment (EROI) of the wind potential is evaluated. Finally, a top-down limitation on kinetic energy available in the atmospheric boundary layer is imposed.
With these constraints wind farm designs are optimized in order to maximize the net energy flux. We find that the global wind potential is substantially lower than previously established when both physical limits and a high cut-off EROI>10 is applied. Several countries’ potentials are below what is needed according to 100% renewable energy studies.
ABSTRACT
Research in stakeholder management has theorized extensively the prioritization of stakeholders as a key dynamic of firms’ value creation, but has paid less attention to the organizational ...practices involved in the process of deciding ‘who and what really counts.’ We examine changes underpinning managers’ prioritization of stakeholders and focus on how managers’ attention to salient stakeholders is represented and communicated in a firm's accounting and reporting system. We study the emergence and development of Social Return on Investment (SROI): an accounting methodology intended to permit managers both to incorporate stakeholders’ voices and to communicate the social value created by the firm for those stakeholders. We find that the ability of SROI to account for specific stakeholders, thus categorizing them as salient for the firm, is shaped by managers’ epistemic beliefs and by the organization's material conditions. Our findings contribute to stakeholder theory by showing that the prioritization of stakeholders is not solely a managerial decision, but instead is dependent on the construction of an appropriate accounting and reporting system, as shaped by managers’ epistemic beliefs and by the organization's material conditions.
Recurring summer cyanobacteria blooms in the Baltic Sea has gained academic interests for decades. The harvest of wild cyanobacteria, for example, Nodularia spumigena, during summer blooms in the ...Baltic Sea has been studied in the past but lacked evaluation for environmental and economic performances. This study provides a first‐hand assessment of environmental and economic performance from an energy perspective, using energy return on investment (EROI) as evaluation method where harvest of biomass and the downstream conversion of biomass to biogas and biofertilizer are considered for Gotland, Sweden. Energy analysis results indicate fuel consumption during harvest and transport operations to be the major energy consumer. Traditional sailing boats have been suggested as an alternative. Overall, when considering only biogas yield and usage of sailing boats, a break‐even EROI of 1 is achieved. When including biofertilizer as product, a breakeven EROI of 1 is also achieved. Depending upon the biomass concentration in the Baltic Sea at the time of harvest, an EROI > 6 is possible, surpassing the economic viability EROI benchmark of 3, indicating the importance of nutrient recovery as the driver for harvest of wild cyanobacteria biomass during blooms in the Baltic Sea. This article met the requirements for a gold‐gold JIE data openness badge described at http://jie.click/badges.
A high gas production rate is critical for commercial exploitation of hydrate. Most marine hydrates deposit in the silty or clay sediments with low permeability, and gas production rate is low. ...Herein, a novel deployment of well, radial three-branch horizontal well was numerically investigated to enhance the gas production. A 3D geological model was established based on field trial in the Shenhu Area of the South China Sea. The simulation showed similar gas and water production for single and multi-branch horizontal wells with same length of 250 m. The depth in which well deployed dramatically affects the gas and water production, and which increases with the length of multi-branch well. Meanwhile the ratio of free gas originally distributed in three-phase and gas layers also increases with the length, which is 50% for 1200 m well. The interference around the intersection of branches enhances temperature recovery and the dissociation of underlying hydrates. The standard energy return on investment analysis shows that the economic potential increases linearly with the length of multi-branch well and obviously depends on the content of initial free gas. However, the production balances investment confines only to tens or hundreds of days for all model scenarios.
•A novel radial three-branch horizontal well is adopted to investigate the enhancement of gas production from hydrate.•Depth of multi-branch well (various contact formation) highly affects gas production.•The deployment of the horizontal well within three-phase layer is feasible for high gas production.•Interference of branches enhances temperature recovery rather than gas recovery.•Cost-benefit balance is analyzed and further technical improvement is needed to meet the economic criterion.
Social enterprises are being promoted as responsive and innovative way to deliver public services. As part of this promotion, these organizations are being required to demonstrate the social and ...economic value they generate. Social return on investment (SROI) is a performance measurement tool currently being encouraged to capture this impact. This paper draws on survey and interview data to analyse how SROI is used and understood in health and social care settings. It indicates that despite being accepted as an internationally recognized measurement tool for social enterprise, SROI is underused and undervalued due to practical and ideological barriers.
PDF
