The sustainable global energy economy: Hydrogen or silicon?

A sustainable global silicon energy economy is proposed as a potential alternative to the hydrogen economy. This first visualisation of a silicon energy economy is based on largescale and carbon-neutral metallic silicon production from major smelters in North Africa and elsewhere, supplied by desert silica sand and electricity from extensive solar generating systems. The resulting “fuel silicon” is shipped around the world to emission-free silicon power stations for either immediate electricity generation or stockpiling. The high energy density of silicon and its stable storage make it an ideal material for maintaining national economic functioning through security of base load power supply from a renewable source. This contrasts with the present situation of fossil fuel usage with its associated global warming and geopolitical supply uncertainties. Critical technological requirements for the silicon economy are carbon-neutral silicon production and the development of efficient silicon-fired power stations capable of high-temperature rapid oxidation of fuel silicon. A call is made for the development of research effort into these specific engineering issues, and also with respect to large-scale economical solar power generation

The economic potential for rainfed agrivoltaics in groundwater stressed regions

Agrivoltaics co-locate crops with solar photovoltaics (PV) to provide sustainability benefits across land, energy and water systems. Policies supporting a switch from irrigated farming to rainfed, grid-connected agrivoltaics in regions experiencing groundwater stress can mitigate both groundwater depletion and CO2 from electricity generation. Here, hydrology, crop, PV and financial models are integrated to assess the economic potential for rainfed agrivoltaics in groundwater stressed regions. The analysis reveals 11.2-37.6 PWh/yr of power generation potential, equivalent to 40-135% of the global electricity supply in 2018. Almost 90% of groundwater depletion in 2010 (~150 km3) occurred where the levelized cost for grid-connected rainfed agrivoltaic generation are 50-100 USD/MWh. Potential revenue losses following the switch from irrigated to rainfed crops represents 0-34% of the levelized generation cost. Future cost-benefit analysis must value the avoided groundwater stress from the perspective of long-term freshwater availability

How does bioenergy compare with other land-based renewable energy sources globally?

The potential power generation from land-based bioenergy is predicted globally using a computer model. Simultaneous consideration of land use, cost and carbon restrictions enables practical evaluation of net power output. Comparisons are made with wind and solar power, and a sensitivity analysis is used to explore the effects of different policy assumptions. Biomass is shown to offer only moderate power-generating potential, and would satisfy less than half of current demand even if all suitable existing arable land were used to grow bioenergy crops. However, bioenergy can be cheap to generate given current economics, and is able to remove atmospheric carbon in some cases if coupled with carbon capture and storage. Wind turbines are able to provide more power globally, but photovoltaic solar panels are the only source considered with the potential to satisfy existing demand. Since land-based bioenergy is also restricted by the need to grow food for an expanding population, and technological developments are likely to greatly increase the viability of other renewable sources, the role of land-based bioenergy appears relatively limited and short-term

The potential land requirements and related land use change emissions of solar energy

Although the transition to renewable energies will intensify the global competition for land, the potential impacts driven by solar energy remain unexplored. In this work, the potential solar land requirements and related land use change emissions are computed for the EU, India, Japan and South Korea. A novel method is developed within an integrated assessment model which links socioeconomic, energy, land and climate systems. At 25-80% penetration in the electricity mix of those regions by 2050, we find that solar energy may occupy 0.5-5% of total land. The resulting land cover changes, including indirect effects, will likely cause a net release of carbon ranging from 0 to 50 gCO(2)/kWh, depending on the region, scale of expansion, solar technology efficiency and land management practices in solar parks. Hence, a coordinated planning and regulation of new solar energy infrastructures should be enforced to avoid a significant increase in their life cycle emissions through terrestrial carbon losses.Funding was provided by Ministerio de Economia, Industria y Competitividad, Gobierno de Espana (Grant No. MDM-2017-0714), Horizon 2020 (Grant Nos. 642260, 821105), Ministerio de Ciencia, Innovacion y Universidades (Grant No. RTI2018-093352-B-I00) and Eusko Jaurlaritza (Grant No. PRE_2017_2_0139)

Increased Panel Height Enhances Cooling for Photovoltaic Solar Farms

Solar photovoltaic (PV) systems suffer substantial efficiency loss due to environmental and internal heating. However, increasing the canopy height of these systems promotes surface heat transfer and boosts production. This work represents the first wind tunnel experiments to explore this concept in terms of array flow behavior and relative convective heat transfer, comparing model solar arrays of varied height arrangements - a nominal height, extended height, and a staggered height configuration. Analyses of surface thermocouple data show average Nusselt number () to increase with array elevation, where panel convection at double height improved up to 1.88 times that of the nominal case. This behavior is an effect of sub-array entrainment of high velocity flow and panel interactions as evidenced through flow statistics and mean kinetic energy budgets on particle image velocimetry (PIV) data. The staggered height arrangement encourages faster sub-panel flow than in the nominal array. Despite sub-array blockage due to the lower panel interaction, heat shedding at panel surfaces promotes improvements on over 1.3 times that of the nominal height case

Wind Power Development: Opportunities and Challenges

In this study, the prospects of wind power at the global level are reviewed. Existing studies indicate that the earth’s wind energy supply potential significantly exceeds global energy demand. Yet, only 1% of the global electricity demand is currently derived from wind power despite 40% annual growth in wind generating capacity over the last 25 years. More than 98% of total current wind power capacity is installed in the developed countries plus China and India. Existing studies estimate that wind power could supply 7% to 34% of global electricity needs by 2050. Wind power faces a large number of technical, financial, institutional, market and other barriers. To overcome these, many countries have employed various policy instruments, including capital subsidies, tax incentives, tradable energy certificates, feed-in tariffs, grid access guarantees and mandatory standards. Besides these policies, climate change mitigation initiatives resulting from the Kyoto Protocol (e.g., CO2-emission reduction targets in developed, the Clean Development Mechanism in developing countries) have played a pivotal role in promoting wind power.wind energy, renewable energy, electricity grids

Economic Analysis of Feed-in Tariffs for Generating Electricity from Renewable Energy Sources

Feed-in tariffs, renewable energy

Lamb growth and pasture production in agrivoltaic production system

Grasslands and croplands located in temperate agro-ecologies are ranked to be the best places to install solar panels for maximum energy production. Therefore, agrivoltaic systems (agricultural production under solar panels) are designed to mutually benefit solar energy and agricultural production in the same location for dual-use of land. However, both livestock farmers and energy companies require information for the application of efficient livestock management practices under solar panels. Therefore, this study was conducted to compare lamb growth and pasture production under solar panels and in open pastures in Corvallis, Oregon in spring 2019 and 2020. Averaged across the grazing periods, weaned Polypay lambs grew at 120 and 119 g/head/d under solar panels and open pastures, respectively in spring 2019 (P=0.90). Although a higher stocking density (36.6 lambs/ha) at the pastures under solar panels was maintained than open pastures (30 lambs/ha) in the late spring period, the liveweight production between grazing under solar panels (1.5 kg ha/d) and open pastures (1.3 kg ha/d) were comparable (P=0.67). Similarly, lambs liveweight gains and liveweight productions were comparable in both pasture types (all P>0.05). The daily water consumption of the lambs in spring 2019 were similar during early spring, but lambs in open pastures consumed 0.72 l/head/d more water than those grazed under solar panels in the late spring period (P<0.01). However, no difference was observed in water intake of the lambs in spring 2020 (P=0.42) The preliminary results from our grazing study indicated that grazing under solar panels can maintain higher carrying capacity of pasture toward summer, and land productivity could be increased up to 200% through combining sheep grazing and solar energy production on the same land. More importantly, solar panels may provide a more animal welfare friendly environment for the grazing livestock as they provide shelter from sun and wind. Key Words: agrivoltaics; lamb growth; solar farming; pasture productio