• Energy Research
• 13. Climate action close
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• Karlsruhe Institute of Technology close

Abstract The storage of heat in aquifers, also referred to as Aquifer Thermal Energy Storage (ATES), bears a high potential to bridge the seasonal gap between periods of highest thermal energy demand and supply. With storage temperatures higher than 50 °C, High-Temperature (HT) ATES is capable to facilitate the integration of (non-)renewable heat sources into complex energy systems. While the complexity of ATES technology is positively correlated to the required storage temperature, HT-ATES faces multidisciplinary challenges and risks impeding a rapid market uptake worldwide. Therefore, the aim of this study is to provide an overview and analysis of these risks of HT-ATES to facilitate global technology adoption. Risk are identified considering experiences of past HT-ATES projects and analyzed by ATES and geothermal energy experts. An online survey among 38 international experts revealed that technical risks are expected to be less critical than legal, social and organizational risks. This is confirmed by the lessons learned from past HT-ATES projects, where high heat recovery values were achieved, and technical feasibility was demonstrated. Although HT-ATES is less flexible than competing technologies such as pits or buffer tanks, the main problems encountered are attributed to a loss of the heat source and fluctuating or decreasing heating demands. Considering that a HT-ATES system has a lifetime of more than 30 years, it is crucial to develop energy concepts which take into account the conditions both for heat sources and heat sinks. Finally, a site-specific risk analysis for HT-ATES in the city of Hamburg revealed that some risks strongly depend on local boundary conditions. A project-specific risk management is therefore indispensable and should be addressed in future research and project developments.

Abstract Thermal conductivity and thermal borehole resistance are basic parameters for the technical and sustainable design of closed ground source heat pump (GSHP) systems. One of the most common methods to determine these parameters is the thermal response test (TRT). The response data measured are typically evaluated by the Kelvin line source equation which does not consider all relevant processes of heat transfer in the subsurface. The approach only considers conductive heat transfer from the borehole heat exchanger (BHE) and all transport effects are combined in the parameters of effective thermal conductivity and thermal borehole resistance. In order to examine primary effects in more detail, a sensitivity study based on numerically generated TRT data sets is performed considering the effects of (1) the in-situ position of the U-shaped pipes of borehole heat exchangers (shank spacing), (2) a non-uniform initial thermal distribution (such as a geothermal gradient), and (3) thermal dispersivity. It will be demonstrated that the shank spacing and the non-uniform initial thermal distribution have minor effects (less than 10%) on the effective thermal conductivity and the determined borehole resistance. Constant groundwater velocity with varying thermal dispersivity values, however, has a significant influence on the thermal borehole resistance. These effects are even more pronounced for interpreted effective thermal conductivity which is overestimated by a factor of 1.2–2.9 compared to the real thermal conductivity of the saturated porous media.

The bigger picture Renewable energy technologies are necessary to maintain secure energy supplies and limit the impacts of climate change. Developments of these technologies are mostly planned purely based on economic criteria, but this can lead to resistance in local communities. Among the diverse renewable technologies, especially onshore wind turbines may negatively affect the scenicness of beautiful landscapes. We analyze how cost-efficient local energy systems could be impacted through public opposition toward onshore wind. In doing so, we draw on a database of public evaluation of landscape beauty across Germany. In the energy systems of German municipalities with high scenicness, onshore wind would mainly be replaced by solar photovoltaics. Depending on the location, the local energy systems may be associated with a significant increase in costs and CO$_{2}$ emissions. These insights can support local and national stakeholders in making decisions relating to energy and climate policy. Summary Local resistance often hinders renewable energy technology developments, especially for onshore wind. In decentralized energy systems, the landscape impact of wind turbines or transmission lines is a key barrier to public acceptance. By using landscape scenicness as a proxy for public acceptance, we quantify its impact on the optimal energy systems of 11,131 German municipalities. In municipalities with high scenicness, it is likely that onshore wind will be rejected, leading to higher levelized costs of energy by up to about 7 €-cent/kWh. Onshore wind would be replaced mainly by solar photovoltaics and imports, and the cost-optimal energy systems would be associated with higher CO$_{2}$ emissions of up to about 200 gCO$_{2}$/kWh compared with an average of around 50 gCO$_{2}$/kWh. The findings help to identify municipalities where public resistance to onshore wind could be particularly high and support the scientific and policy debate about the location of onshore wind farms.

Induction of PM2.5-associated lung cancer in response to EGFR-tyrosine kinase inhibitors (EGFR-TKI) remains unclear. Polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives (oxygenated PAHs: OPAHs and azaarenes: AZAs) were characterized in fine particulates (PM2.5) emitted from indoor coal combustion. Samples were collected in Xuanwei (Yunnan Province), a region in China with a high rate of lung cancer. Human lung adenocarcinoma cells A549 (with wild-type EGFR) and HCC827 (with EGFR mutation) were exposed to the PM2.5, followed by treatment with EGFR-TKI. Two samples showed significant and dose-dependent reduction in the cell viability in A549. EGFR-TKI further demonstrated significantly decreased in cell viability in A549 after exposure to the coal emissions. Chrysene and triphenylene, dibenzo[a,h]anthracene, benzo[ghi]perylene, azaarenes and oxygenated polycyclic aromatic hydrocarbons (carbonyl-OPAHs) were all associated with EGFR-TKI-dependent reduced cell viability after 72-h exposure to the PM2.5. The findings suggest the coal emissions could influence the response of EGFR-TKI in lung cancer cells in Xuanwei.

Abstract. A 5-year greenhouse gas (GHG) exchange study of the three major gas species (CO2, CH4 and N2O) from an intensively managed permanent grassland in Switzerland is presented. Measurements comprise 2 years (2010 and 2011) of manual static chamber measurements of CH4 and N2O, 5 years of continuous eddy covariance (EC) measurements (CO2–H2O – 2010–2014), and 3 years (2012–2014) of EC measurement of CH4 and N2O. Intensive grassland management included both regular and sporadic management activities. Regular management practices encompassed mowing (three to five cuts per year) with subsequent organic fertilizer amendments and occasional grazing, whereas sporadic management activities comprised grazing or similar activities. The primary objective of our measurements was to compare pre-plowing to post-plowing GHG exchange and to identify potential memory effects of such a substantial disturbance on GHG exchange and carbon (C) and nitrogen (N) gains and losses. In order to include measurements carried out with different observation techniques, we tested two different measurement techniques jointly in 2013, namely the manual static chamber approach and the eddy covariance technique for N2O, to quantify the GHG exchange from the observed grassland site. Our results showed that there were no memory effects on N2O and CH4 emissions after plowing, whereas the CO2 uptake of the site considerably increased when compared to pre-restoration years. In detail, we observed large losses of CO2 and N2O during the year of restoration. In contrast, the grassland acted as a carbon sink under usual management, i.e., the time periods 2010–2011 and 2013–2014. Enhanced emissions and emission peaks of N2O (defined as exceeding background emissions 0.21 ± 0.55 nmol m−2 s−1 (SE = 0.02) for at least 2 sequential days and the 7 d moving average exceeding background emissions) were observed for almost 7 continuous months after restoration as well as following organic fertilizer applications during all years. Net ecosystem exchange of CO2 (NEECO2) showed a common pattern of increased uptake of CO2 in spring and reduced uptake in late fall. NEECO2 dropped to zero and became positive after each harvest event. Methane (CH4) exchange fluctuated around zero during all years. Overall, CH4 exchange was of negligible importance for both the GHG budget and the carbon budget of the site. Our results stress the inclusion of grassland restoration events when providing cumulative sums of C sequestration potential and/or global warming potential (GWP). Consequently, this study further highlights the need for continuous long-term GHG exchange observations as well as for the implementation of our findings into biogeochemical process models to track potential GHG mitigation objectives as well as to predict future GHG emission scenarios reliably.

AbstractAgriculture is a significant source of GHGsglobally and ruminant livestock animals are one of the largest contributors to these emissions, responsible for an estimated 14% of GHGs (CH4and N2O combined) worldwide. A large portion of GHG fluxes from agricultural activities is related to CH4 emissions from ruminants. Both direct and indirect methods are available. Direct methods include enclosure techniques, artificial (e.g. SF6) or natural (e.g. CO2) tracer techniques, and micrometeorological methods using open-path lasers. Under the indirect methods, emission mechanisms are understood, where the CH4 emission potential is estimated based on the substrate characteristics and the digestibility (i.e. from volatile fatty acids). These approximate methods are useful if no direct measurement is possible. The different systems used to quantify these emission potentials are presented in this chapter. Also, CH4 from animal waste (slurry, urine, dung) is an important source: methods pertaining to measuring GHG potential from these sources are included.