Energy

Recent studies show that tropical hydroelectric reservoirs may be responsible for substantial greenhouse gas emissions to the atmosphere, yet emissions from the surface of released water downstream of the dam are poorly characterized if not neglected entirely from most assessments. We found that carbon dioxide (CO₂) emission downstream of Kariba Dam (southern Africa) varied widely over different timescales and that accounting for downstream emissions and their fluctuations is critically important to the reservoir carbon budget. Seasonal variation was driven by reservoir stratification and the accumulation of CO₂ in hypolimnetic waters, while subdaily variation was driven by hydropeaking events caused by dam operation in response to daily electricity demand. This "carbopeaking" resulted in hourly variations of CO₂ emission up to 200% during stratification. Failing to account for seasonal or subdaily variations in downstream carbon emissions could lead to errors of up to 90% when estimating the reservoir’s annual emissions. These results demonstrate the critical need to include both limnological seasonality and dam operation at subdaily time steps in the assessment of carbon budgeting of reservoirs and carbon cycling along the aquatic continuum.

Due to their cooling ability, sustainable roofing configurations, such as green and cool roofs, have the potential to increase solar panel yield, which is temperature dependent. However, the influence of sustainable roofing configurations on panel yield is not yet considered in rooftop photovoltaic (PV) planning models; thus, the significance of these integrated systems cannot be evaluated. In order to quantify the potential benefits of sustainable rooftops on solar energy, the first goal of this study is to develop a method that systematically accounts for roof surface characteristics in the simulation of PV panel energy yield. To do so, a rooftop energy balance model is linked with a physically-based solar energy model (the System Advisor Model, SAM) to quantify the energy yield of PV installations on sustainable roofing configurations. Roof surface temperatures are first estimated using non-linear energy balance equations, then integrated into a revised version of SAM to simulate energy yield. This new method improves the accuracy of PV yield simulations, compared to prior assumptions of roof surface temperature equal to ambient temperature. This updated model is used for the second goal of the study, to understand how four roofing configurations (black membrane, rock ballasted, white membrane, and vegetated) influence PV panel yield, which is currently not well understood in cooler climates. For a flat rooftop PV installation near Zurich, Switzerland (temperate climate), results show that, compared to a conventional roof, green roofs can increase annual PV energy yield, on average, by 1.8%, whereas cool roofs can increase it by 3.4%. For the case-study installation, an inverse correlation between the 95th-quantile roof surface temperature and the PV energy yield was identified; an increase of 1 °C leads to a 71 kWh reduction in energy yield per year. Overall, cool roofs outperform green roofs in terms of increases in PV energy yield; however, potential improvements of both systems are non-negligible, even in relatively cooler climate regions like Switzerland. By providing a systematic method to evaluate the influence of the roofing configuration on PV energy yield, solar energy planners are able to differentiate between the benefits of traditional and sustainable rooftop configurations - the first step towards the coupling of distributed energy and sustainable building systems. In the future, this integrated method could be used as part of a holistic evaluation of the environmental, economic, and social objectives of green and cool roofs, as well as, other infrastructure systems.

Policies that mandate the adoption of renewable energy innovations could ensure their widespread adoption. Yet, such policies may not be implemented if they face strong opposition from the public, especially when strong negative emotions are at the core of opposition. In a field experiment (N = 97), we investigated people's emotional responses to two policy options aimed at increasing the adoption of heat pumps in a neighbourhood in the city of Groningen: a campaign promoting the voluntary adoption of heat pumps versus a regulation that mandates the adoption of heat pumps. In line with reactance theory, the policy option mandating the adoption of heat pumps was perceived to threaten people's freedom more and, in turn, caused stronger negative and weaker positive emotions than the policy option promoting voluntary adoption. Yet, emotions towards the policy options were also related to people's values, providing partial support for the Value-Innovation-Congruence model of Emotional responses. Stronger egoistic values were related with stronger negative emotions, particularly towards the policy option mandating adoption, while stronger biospheric values were related with stronger positive emotions, but only towards the policy option promoting voluntary adoption. Emotions, in turn, were related with acceptability of the policy options. Our findings imply that measures aimed at increasing positive emotions and reducing negative emotions towards policies aimed at increasing the adoption of energy innovations could profit from considering people's core values.

Under the U.S. National Environmental Policy Act (NEPA), energy infrastructure projects that are permitted by federal agencies require preparation and publication of an environmental impact assessment. However, fifty years after the passage of NEPA, agencies’ compliance behaviors, and how these behaviors might shape the risks associated with energy infrastructure, remain largely unexplored. Here, we consider how assessment documents from forty-six of the largest U.S. natural gas pipeline mega-projects address landslide risks. Using a series of text mining and content analysis methods, we evaluate the prevalence of recycled text across assessments. We find that text similarity does not correspond closely to reported risk levels – in many cases, common verbiage is used and only project-specific details (e.g., locations, numeric figures) are substituted. While such approaches likely expedite preparation of assessments and facilitate knowledge transfer between projects, we argue that common text potentially hinders clear communication of differential risks to decision-makers and the public, who may lack the technical expertise to contextualize the magnitude and severity of reported figures. In light of ongoing policy efforts to streamline lengthy and costly energy infrastructure permitting processes under NEPA, it is vital that such efforts do not undermine the risk communication requirements of the review process.