The importance of gas-aerosol interactions in policy making

In current emission comparisons, the most cost effective method is one which employs multicomponent climate change mitigation strategies. These strategies involve analyzing both the direct and indirect effects of various linked emissions. However, the information of indirect effects between most gaseous pollutants and aerosols is absent. Shindell et al. (2009) took two approaches to calculate the impact of emissions on aerosols and the influence of these on radiative forcing. They found that the global warming potential (GWP) is substantially larger when the direct effects of aerosol interactions are considered and increases further when aerosol-cloud interactions are taken into account. Therefore, as atmospheric chemistry links methane, ozone, and aerosols, the policies regarding multigas mitigation should take gas-aerosol interactions into consideration.  Alyson Stark
Shindell, D., Faluvegi, G., Koch, D., Schmidt, G., Unger, N., Bauer, S., 2009. Improved Attribution of Climate Forcing to Emissions. Science 326: 716-718.

Shindell et al. relied heavily on averaged radiative forcing (RF) to compare various emissions and to estimate GWP. To find the response of atmospheric composition to both the collective and individual effects of emissions, the researchers calculated abundance based RF, which measured the effects of all emissions changing concurrently, and emissions based forcing, which instead attributed the response to a specific pollutant. Using these two techniques, Shindell et al. estimated several 100-year GWPs. These computations demonstrated that, with the absence of aerosol responses, the results were similar to previous studies. However, once the radiative effects are regarded, the GWP becomes larger in both methane and carbon monoxide (CO). Compared to the initial situation with no aerosol, the possible methane emission range increases, from approximately 25 to a range of 25-40 over a 100 year horizon. Similarly, the CO emissions initially begin at a 1-3 range and increases to a 3-8 range.  However,  the accuracy of these values is essential, and it there still remains much uncertainty in the predictions. For example, increases in these values also increases carbon dioxide, which perpetuates higher GWPs, and leads to more uncertain policymaking. 

The Economic Utility of Photovoltaic Systems for Arid Region Communities

Qoaider and Steinbrecht (2009) examine the possibility of PV system use for arid region communities by comparing potential costs of both PV and genset systems for the Kalabash village, which lies south of the Tropic of Cancer. This area is an optimal candidate for a photovoltaic (PV) System due to high solar energy potential. The energy demand of the village is the highest during the summer months because there is a greater demand for water pumping as the temperatures are higher and the lake water is low. These conditions peak in the month of July, so July was chosen as the design month to prepare for a “worst case scenario”. Qoaider and Steinbrecht found that the genset systems require expensive operating and maintenance costs, and that the PV system is a favorable alternative because no fossil fuel is required, giving rise to a system that is less damaging to the surrounding environment.—Aly Stark
  Qoaider, L. and Steinbrecht, D., 2009. Photovoltaic systems: A cost competitive option to supply energy to off-grid agricultural communities in arid regions. Applied Energy 87, 427–435

As fuel prices rise, more isolated farming communities dependent on electric irrigation will require lower cost energy. Currently, the most common electrification mechanism in off-grid areas is the diesel generator (genset), which requires significant amounts of fossil fuel to operate. However, it is possible that photovoltaic (PV) systems may soon be a more economically competitive way to provide field irrigation and village energy. These systems are not dependent on fuel, which reduces environmental degradation.  Also, low operating and maintenance requirements allow PV systems to be realistic in areas of remote location and relatively untrained labor. These systems have the potential to have higher operating hours, further encouraging sustainable development of the village. However, whether or not the PV systems are economically feasible and a current competitive option will dictate their use.
After assessing the energy demand, Qoaider and Steinbrecht utilized a pre-design of the PV system to estimate size and costs. However, they found that the presizing method, which considered energy demands and costs from PV array, battery bank in the village, field inverter, and village inverter, would perform excellently in the winter months, but would decrease in efficiency and yield in the summer months. The system was then enlarged by 11% (from 1939 kWp to 2184 kWp) to satisfy the actual amount of energy needed for the year. While this proposed system size results in overproduction during the winter months, Qoaider and Steinbrecht imply that the additional energy can be used to advance small farming industries and handicrafts.  The shortcomings of the PV system include the need for a power transmission line, sub generators, and high initial investment costs.
Qoaider and Steinbrecht found that compared to the proposed costs of a genset systems for the region, a PV system is more economically efficient. Although fuel is currently heavily subsidized in many developing nations, the calculations done in this research employed real market value fuel prices that would likely occur if the subsidy ceased to exist. This fuel cost component, along with extensive operation, monitoring, and maintenance requirements, drives up the cost of current genset systems. Additionally, genset systems are operable for limited hours, while PV systems have a greater capacity for continual energy production. In terms of longevity, the PV systems are anticipated to have a lifetime of 25 years, with inverters changed once during that time, which cuts the costs and labor of replacements.  Thus should fuel prices be increasing and consistent with real market value prices, Qoaider and Steinbrecht conclude that PV systems are more economically competitive than diesel driven genset systems.—Aly Stark