Energy and CO2 implications of decarbonization strategies for China beyond efficiency: Modeling 2050 maximum renewable resources and accelerated electrification impacts

Energy efficiency has played an important role in helping China achieve its domestic and international energy and climate change mitigation targets, but more significant near-term actions to decarbonize are needed to help China and the world meet the Paris Agreement goals. Accelerating electrification and maximizing supply-side and demand-side renewable adoption are two recent strategies being considered in China, but few bottom-up modeling studies have evaluated the potential near-term impacts of these strategies across multiple sectors. To fill this research gap, we use a bottom-up national end-use model that integrates energy supply and demand systems and conduct scenario analysis to evaluate even lower CO2 emissions strategies and subsequent pathways for China to go beyond cost-effective efficiency and fuel switching. We find that maximizing non-conventional electric and renewable technologies can help China peak its national CO2 emissions as early as 2025, with significant additional CO2 emission reductions on the order of 7 Gt CO2 annually by 2050. Beyond potential CO2 reductions from power sector decarbonization, significant potential lies in fossil fuel displaced by renewable heat in industry. These results suggest accelerating the utilization of non-conventional electric and renewable technologies present additional CO2 reduction opportunities for China, but new policies and strategies are needed to change technology choices in the demand sectors. Managing the pace of electrification in tandem with the pace of decarbonization of the power sector will also be crucial to achieving CO2 reductions from the power sector in a scenario of increased electrification

Links between soil microbial communities and plant traits in a species-rich grassland under long-term climate change

Climate change can influence soil microorganisms directly by altering their growth and activity but also indirectly via effects on the vegetation, which modifies the availability of resources. Direct impacts of climate change on soil microorganisms can occur rapidly, whereas indirect effects mediated by shifts in plant community composition are not immediately apparent and likely to increase over time. We used molecular fingerprinting of bacterial and fungal communities in the soil to investigate the effects of 17 years of temperature and rainfall manipulations in a species‐rich grassland near Buxton, UK. We compared shifts in microbial community structure to changes in plant species composition and key plant traits across 78 microsites within plots subjected to winter heating, rainfall supplementation, or summer drought. We observed marked shifts in soil fungal and bacterial community structure in response to chronic summer drought. Importantly, although dominant microbial taxa were largely unaffected by drought, there were substantial changes in the abundances of subordinate fungal and bacterial taxa. In contrast to short‐term studies that report high resistance of soil fungi to drought, we observed substantial losses of fungal taxa in the summer drought treatments. There was moderate concordance between soil microbial communities and plant species composition within microsites. Vector fitting of community‐weighted mean plant traits to ordinations of soil bacterial and fungal communities showed that shifts in soil microbial community structure were related to plant traits representing the quality of resources available to soil microorganisms: the construction cost of leaf material, foliar carbon‐to‐nitrogen ratios, and leaf dry matter content. Thus, our study provides evidence that climate change could affect soil microbial communities indirectly via changes in plant inputs and highlights the importance of considering long‐term climate change effects, especially in nutrient‐poor systems with slow‐growing vegetation

Governing Yield Modes for Common Bolted and Nailed Wood Connections

Connections in wood structures are important when designing for ductility. The 1997 Uniform Building Code has taken this into consideration when designating wind and earthquake load duration factors for connections. Factors of 1.6 or 1.33 may be applied to the connection strength, depending on the type of yield mode exhibited by the connection, which may be determined from the yield limit equations supplied in the National Design Specification for Wood Construction (NDS). The NDS provides the designer with multiple tables containing capacities for various common connections. Unfortunately, yield modes are not published along with tabulated capacities. Therefore, the designer must carry out potentially cumbersome calculations using the NDS yield limit equations simply to determine the governing yield mode before an appropriate Uniform Building Code load duration factor can be applied. In this paper, several NDS tables are extended to include capacity and yield mode, smaller side member thickness configurations are added to the existing nail/spike tables, and a useful toe-nail table is provided. The overall purpose of these tables is to accelerate the design process by eliminating time-consuming calculations

Reliability-Based System Factor for Serviceability Design of Wood Floors

A structural analysis model for parallel-member wood joist floors is developed that includes the effect of component creep. Viscoelastic material models are calibrated using the data from a recently completed experimental program conducted as part of this overall study. Using this system model, deflection serviceability reliability analyses of parallel-member wood systems, including the effects of creep deformation, are conducted. Stochastic load models are used to simulate the time-varying nature of applied loads. Multiple limit state definitions for deflection serviceability of parallel-member wood floors are considered. Monte Carlo simulation is used to evaluate limit state probabilities. Reliability indices for current serviceability design provisions are also evaluated, and a serviceability system factor for Load and Resistance Factor Design (LRFD) is recommended

Thermal Effects on Load-Duration Behavior of Lumber. Part II: Effect of Cyclic Temperature

The effect of a cyclic thermal loading on the load-duration behavior of structural lumber in bending is presented. Select Structural and No. 2 grade Douglas-fir nominal 2 by 4 beams were tested under a constant bending load to determine time-to-failure. Two cyclic temperature environments were used in the investigation: 73 F to 100 F and 73 F to 130 F on a 24-hour cycle with a constant 50% relative humidity. An exponential damage accumulation model with a temperature factor was used to predict the observed times-to-failure. The damage model originally was fitted and calibrated using load-duration data from equivalent lumber samples subjected to constant temperature environments. The model predicted quite well the observed times-to-failure in the cyclic temperature environments. This is quantified using a standard errors analysis between the model predictions and the observed cyclic temperature data. These errors are comparable to those observed with the constant temperature data which were used to determine the model constants

Moisture Effects On Load-Duration Behavior of Lumber. Part II. Effect of Cyclic Relative Humidity

The effect of cyclic moisture conditions on the load-duration behavior of structural lumber is presented. Select Structural and No. 2. Douglas-fir nominal 2 by 4 specimens were tested in bending in two cyclic relative humidity (RH) environments: 35% to 95% RH on 24- and 96-hour cycles. A constant temperature of 73 F was maintained in both tests. Constant bending loads based on the 15th percentile of the static strength distributions for each grade at 73 F and 50% RH were used to load the beams. The load-duration behavior in the two cyclic RH environments is compared to previously reported results observed from three constant RH environments (35%, 50%, and 95% RH at 73 F). Analysis of test results indicated a trend toward shorter times-to-failure in cyclic RH conditions as compared to constant RH conditions. The effect, however, was no more evident in the No. 2 specimens than in the Select Structural specimens. To predict the load-duration behavior, an existing damage accumulation model was modified to account for the effect of changing moisture contents on the long-term strength of structural lumber. The developed model was found to predict the observed behavior quite well

Thermal Effects On Load-Duration Behavior Of Lumber. Part I. Effect Of Constant Temperature

The effect of constant thermal loadings on the load-duration relationships for structural lumber in bending is presented. Select Structural and No. 2 grade Douglas-fir nominal 2 by 4 (38.1 mm by 88.9 mm) beams were tested in bending under constant load. Constant temperature environments of 73 F, 100 F, and 130 F (22.8 C, 37.8 C, and 54.4 C) were used in the investigation. A constant 50% relative humidity (RH) was maintained for each temperature. The applied bending loads were based on the 15th percentile of the assumed static strength distributions for each grade at 73 F and 50% RH. An exponential damage accumulation model modified to account for temperature effects is used to define the load-duration response. The results indicate shorter times-to-failure with corresponding higher probabilities of failure for equal levels of mechanical stress as the temperature is increased

Efficacy of Interactive Internet-Based Education in Structural Timber Design

While traditional teaching methods (e.g., real-time, synchronous lectures) have proven effective for training future engineers, the Internet provides an avenue to reinforce the material and augment student learning, comprehension, and retention of material. This paper presents the integration and assessment of a library of interactive instructional modules specifically for a senior-level undergraduate elective course in civil engineering. An ongoing, comprehensive assessment process was implemented in the fall 1999 semester. The results of this quantitative assessment indicate that the use of well designed and pedagogically sound Internet-based supplemental modules provide students with a better understanding of course material. However, when Internet-based content does not promote critical thinking, little increase in the student performance and understanding of the material is realized. Interactive Web-based instruction should not be viewed as a “replacement” to traditional instruction, but rather a tool that provides a broader and more dynamic environment for students with a variety of learning styles

Creep and Creep-Recovery Models for Wood Under High Stress Levels

Forty small clear southern pine specimens were loaded under third-point bending to examine creep and creep-recovery behavior for wood under high stress levels. Stress levels of between 69% and 91% of the predicted static strength were applied for 23 h with 1 h allowed for recovery, and the resulting deflection vs. time behavior was studied. The experimental creep and creep-recovery behavior was modeled using modified power law functions. The results indicate that these functions provide the best fit to both primary and secondary experimental data. The empirical models can be used to simulate the viscoelastic behavior of wood under high stress levels. The simulation will provide a useful tool in future studies to examine duration-of-load (DOL) effect, which is one of the more important factors in wood structural design