The 2020 photovoltaic technologies roadmap

Over the past decade, the global cumulative installed photovoltaic (PV) capacity has grown exponentially, reaching 591 GW in 2019. Rapid progress was driven in large part by improvements in solar cell and module efficiencies, reduction in manufacturing costs and the realization of levelized costs of electricity that are now generally less than other energy sources and approaching similar costs with storage included. Given this success, it is a particularly fitting time to assess the state of the photovoltaics field and the technology milestones that must be achieved to maximize future impact and forward momentum. This roadmap outlines the critical areas of development in all of the major PV conversion technologies, advances needed to enable terawatt-scale PV installation, and cross-cutting topics on reliability, characterization, and applications. Each perspective provides a status update, summarizes the limiting immediate and long-term technical challenges and highlights breakthroughs that are needed to address them. In total, this roadmap is intended to guide researchers, funding agencies and industry in identifying the areas of development that will have the most impact on PV technology in the upcoming years

On the Rocks: Quantifying Storage of Inorganic Soil Carbon on Gravels and Determining Pedon-Scale Variability

The storage and flux of carbon from soils, the planet\u27s third largest carbon pool, strongly influence the global carbon cycle and are essential, but poorly constrained, parameters for global climate models. An estimated 40% of all soil carbon is stored as inorganic carbonate minerals. Despite a recognition of the importance of soil inorganic carbon (SIC) in soil carbon storage, few studies have quantified pedon-scale variability in SIC storage. We examine different stages of carbonate development and accumulation rates between gravelly and non-gravelly soils. Studies often ignore carbonate coatings on gravels in measurements of soil inorganic carbon (SIC). By quantifying and differentiating the fine (\u3c 2 mm) and coarse (\u3e 2 mm) fractions of SIC in the Reynolds Creek Experimental Watershed in southwestern Idaho, we show that gravel coatings contain up to 44% of total SIC at a given site. Among the 26 soil sites examined throughout the watershed, an average of 13% of the total SIC is stored as carbonate coatings within in the gravel fraction. We measured a high level of pedon-scale field variability (up to 220%) among the three sampled faces of 1 m3 soil pits. Analytical error associated with the modified pressure calcimeter (0.001–0.014%) is considerably less than naturally occurring heterogeneities in SIC within the soil profile. This work highlights and quantifies two sources of uncertainty in studies of SIC needed to inform future research. First, in gravelly sites, the \u3e 2 mm portion of soils may store a large percentage of SIC. Second, SIC varies considerably at the pedon-scale, so studies attempting to quantify carbon storage over landscape scales need to consider this variability

Reynolds Creek – A Collection of Near-Surface Soil Organic Carbon (SOC) Maps, GIS/Map Data (2017)

The SOC (Soil Organic Carbon) pool is a large carbon reservoir that is closely linked to climatic drivers. In complex terrain, quantifying SOC storage is challenging due to high spatial variability. Generally, point data is distributed by developing quantitative relationships between SOC and spatially-distributed, variables like elevation. In many ecosystems, remotely sensed information on above-ground vegetation (e.g. NDVI) can be used to predict below-ground carbon stocks. With this research, we evaluated SOC variability in complex terrain and attempt to improve upon SOC models by incorporating hyperspectral and LiDAR datasets

Controls on the Presence and Storage of Soil Inorganic Carbon in a Semi-Arid Watershed

Soil inorganic carbon (SIC) constitutes ∼40–50% of the terrestrial soil carbon and is an integral part of the global carbon cycle. Rainfall is a primary factor controlling SIC accumulation; however, the distribution and hierarchy of controls on SIC development in arid and semi-arid regions is poorly understood. The Reynolds Creek Experimental Watershed (RCEW) in southwestern Idaho is an ideal location to study factors influencing SIC because it spans a wide mean annual precipitation range (235 mm to 900 mm) along a 1,425 to 2,111 m elevation gradient and has soils derived from a wide variety of parent materials (granite, basalt, dust, and alluvium). We collected soil samples along this elevational gradient to understand local controls on SIC distributions. SIC content was quantified at 71 soil pits and/or augered cores collected between approximately 0–1 m depth or until refusal. Consistent with previous studies, we found variations in precipitation governed the presence or absence of SIC; field measurements of the top 1 m of soils confirm little or no SIC in soils receiving \u3e 500 mm in mean annual precipitation. Below this 500 mm threshold, SIC pools varied substantially and significantly between sites. Results showed that 90% of sites (64 sites) contained less than 10 kg m−2 SIC, 7% (5 sites) contained 10–20 kg m−2, and 3% (2 sites) contain between 24 and 29 kg m−2 SIC. The total SIC within RCEW was estimated at ∼5.17 × 105 Mg. After precipitation, slope consistently ranked as the second most important predictor of SIC accumulation in random forest analysis. Wind-blown dust likely contributed to SIC accumulation; prior work indicates an average dust flux rate in RCEW of about 11 ± 4.9 g m−2 year−1. This study provides an initial model predicting SIC distribution and accumulation in a shrub-dominated dryland watershed