Search

Reducing energy consumption from buildings' operations is a sine-qua-non for achieving a future with net-zero emissions. Could urban trees play a role? Several observational and simulation studies demonstrate the effect of vegetation on reduced energy consumption and this study confirms it, this time looking at densely populated areas in diverse climate zones. A comprehensive multi-year monthly electricity consumption data set representative of all of China, together with high-resolution NDVI (Normalized Difference Vegetation Index) data, reveal the relationship between an urban area's greenness and its residents' domestic electricity consumption. Findings show that for every 0.1 increase in the cities' NDVI, urban per-capita residential electricity consumption decreases by 1.76% (95% CI: 1.11–2.42%). This cut in electricity consumption results in life-cycle power-sector CO 2 annual emissions reductions of 23.05–45.52 Mt., equivalent to 2.85–5.63% of China's total residential sector CO 2 emissions in 2020, depending on assumptions on urban population's size and electricity sector's carbon intensity. Moreover, these cities' trees can store 247–284 Mt. CO 2 over 30 years, so the present value of the net benefits, equal to monetized electricity savings plus carbon emissions' reductions and carbon storage minus tree planting and maintenance costs, is positive for 29 Chinese provinces (except Chongqing and Xizang) ranging between US$-0.84 and US$21,000 per tree (−6–156,485 yuan/tree). If not planted exclusively in urban areas but all over China, a carbon price of 267–1339 yuan/ton is needed to ensure the benefits cover the costs of planting and maintaining the trees. • Trees reduce residential electricity consumption and store carbon as they grow. • A 0.1 increase in NDVI saves 1.11%- 2.46% residential electricity consumption. • We quantify trees' costs, CO 2 emissions reductions, and trees' CO 2 storage. • Benefits outweigh city tree planting/maintenance costs in all but two provinces. • Increasing China's NDVI (not just in cities) is cost-effective with low carbon tax. [ABSTRACT FROM AUTHOR]

Highlights: [•] There is a significant CO2 intensity convergence across the world. [•] High GDP growth may accelerate CO2 intensity decline, yet total emissions will grow dramatically. [•] GDP per capita are negatively related to CO2 intensity decline. [•] The potential for carbon intensity reduction is becoming less with the economic development. [•] The conclusions are robust to the possible impact factors such as initial year, and country grouping. [ABSTRACT FROM AUTHOR]

• PV + storage can reduce CO 2 emissions while lowering cost of abatement. • Storage optimal power rating seems to be lower than 25% of PV capacity. • Storage with low energy-to-power ratio is cost effective with lower PV shares. • PV + storage systems would achieve breakeven point with expected costs projections. • Optimal configurations can reduce carbon emissions in the DEC/DEP system up to ~57%. This study explores the performance of the Duke Energy Carolinas/Progress (DEC/DEP) electric power system under one hundred forty-one configurations combining different capacities of utility-scale photovoltaics (PV) and battery energy storage (lithium-ion batteries or BES). The different configurations include PV installations capable of providing 5–25% of the systems energy and batteries with varying duration (energy-to-power ratio) of 2, 4, and 6 h. A production cost model comprised of a day-ahead unit commitment and a real-time economic dispatch simulates the optimal operation of all the generation resources necessary to supply hourly demand and reserve requirements during the year 2016. The model represents in detail the generation fleet of the system, including 221 nuclear, natural gas, coal and hydro power generators with a combined installed capacity of 37.8 GW. Results indicate that: 1) adding BES to a power system that includes PV further reduces carbon dioxide emissions while also lowering the cost of carbon abatement. 2) The optimal power rating of a BES system that supports PV seems to be lower than 25% of the capacity of the PV. 3) BES of short duration (2-h) are more cost-effective (i.e., result in a lower cost of abatement) when the level of PV penetration is low (lower than ~12.5%), while BES of longer duration (6-h) are more cost-effective when there are larger shares of PV. 4) The installation of optimal configurations of PV + BES to reduce carbon emissions in the DEC/DEP system by ~14–57% would increase the levelized cost of electricity (LCOE) ~8–65%. 5) If projections of declining costs for the next decade materialize, the installation of up to 15 GW of PV + 1.88 GW / 3.76 GWh of BES would reduce the LCOE while achieving up to 33% reduction in carbon emissions. [ABSTRACT FROM AUTHOR]