Sten Karlsson

Material constraints for thin-film solar cells

Harnessing solar energy by using photovoltaic cells has the potential to become a major CO2-free energy source. Materials requirements for the solar cells based on four types of thin-film photovoltaics have been estimated and compared with global reserves, resources and annual refining. The use of solar cells based on Cd, Ga, Ge, In, Ru, Se and Te as a major energy-supply technology has severe resource constraints. Other systems such as a-Si without Ge and crystalline silicon do not involve such constraints. For some of these metals, there is the risk of enhanced, environmentally deleterious concentrations in the ecosphere due to leakage from manufacturing, use or waste handling.

On Designing Socio-Ecological Indicators

There is a need for indicators which capture the essential parts of society in the maladjustments of its physical relations to nature. The socio-ecological indicators should contribute to the control mechanisms that are urgently needed if society is to be able to redirect itself to a path of development which is subordinated to sustainable interactions with nature. An analysis of various factors important to the design of socio-ecological indicators is performed here. An important aspect of the socio-ecological indicators is that they will focus on parts situated early in the cause-effect chain. This implies better possibilities for foresights when dealing with the global, complex or diffuse problems in connection to sustainability. The indicators can be useful in many situations: as a support for discussions among decision-makers and the general public, as part of an environmental impact analysis, and as a tool in the evaluation of various plans or projects.

Commuter Route Optimized Energy Management of Hybrid Electric Vehicles

Optimal energy management of hybrid electric vehicles requires a priori information regarding future driving conditions; the acquisition and processing of this information is nevertheless often neglected in academic research. This paper introduces a commuter route optimized energy management system, where the bulk of the computations are performed on a server. The idea is to identify commuter routes from historical driving data, using hierarchical agglomerative clustering, and then precompute an optimal solution to the energy management control problem with dynamic programming; the obtained solution can then be transmitted to the vehicle in the form of a lookup table. To investigate the potential of such a system, a simulation study is performed using a detailed vehicle model implemented in the Autonomie simulation environment for MATLAB/Simulink. The simulation results for a plug-in hybrid electric vehicle indicate that the average fuel consumption along the commuter route(s) can be reduced by 4%-9% and battery usage by 10%-15%.

Closing the Technospheric Flows of Toxic Metals: Modeling Lead Losses from a Lead-Acid Battery System for Sweden

Summary This article investigates technological opportunities to close technospheric flows in a large-scale use of a toxic and scarce metal, lead. It analyzes the lead flows and losses to the environment in a modeled lead-acid battery system for Sweden. The modeled system is built on todays technology for production and recycling of lead and batteries while the recovery of used batteries is varied. The analysis shows that the losses from the production and recycling processes are so low that consumption losses and the recovery rate dominate the total system losses. In a steady state with very high recovery of used batteries, the system losses are small compared to natural lead flows and to the historical lead losses during the industrialization. The modeling assumes that all the secondary lead goes back into the production of new batteries even though in Swedish battery manufacturing today, primary lead dominates the lead supply for lead oxide production. The possibilities for increased secondary lead use in the production of lead oxide are also discussed

The Exergy of Incoherent Electromagnetic Radiation

The exergy in an arbitrary spectrum of incoherent electromagnetic radiation is derived. For each wave vector of the radiation a quality factor is defined. The mean quality factor for black-body radiation (1 - 4/3(T0/T) + 1/3(T0/T)4) is obtained as a special case.

GPS measurement of Swedish car movements for assessment of possible electrification

To enhance the transition to electrified vehicles, such as PHEVs, the use patterns of cars need to be well understood and thus information about individual vehicles movements over longer time periods is needed. This is of major importance for instance for optimal powertrain and battery design, estimation of consumer viability and potential for PHEVs and for assessment of policies for shifting energy use in transport sector from fuel to electricity. Good and publicly available data of this kind is today unfortunately lacking. The aim of this project has been to gather a larger amount of data on the characteristics and distribution of individual movements for privately driven cars in Sweden by measurement with GPS equipment. The logging was performed with commercial equipment containing a GPS unit, including a roof-mounted antenna, and a gprs communication unit. Data logged (2.5 Hz) were: time, position, velocity, and number and id of used satellites. The measurements started in June 2010 and ended in September 2012. The target has been to accomplish good quality measurements of at least 30 days for about 500 representative vehicles. The paper includes a description of the project, an analysis of its representativeness and some car movement statistics for the full results.

Future Redistribution of Cadmium to Arable Swedish Soils A Substance Stock Analysis

This article describes a stock‐based methodology designed to analyze the redistribution of substance stocks to environmental compartments. The methodology is then applied to investigate the requirements and possibilities for avoiding undesired future accumulation of cadmium in Swedish arable soils. A prospective decomposition analysis of human cadmium mobilization is thus performed to estimate the potential amounts that can end up in arable soils through different flows from the cadmium stocks identified. The requirements for cadmium abatement to achieve prescribed goals for accumulation limits are determined and compared with past and current achievements and with the varying qualities of possible abatement methods. A stock‐based methodology adds some important information to traditional scenario techniques based on substance flow analysis. The most obvious is that the fact that stocks are limited actually matters for long‐term accumulation of cadmium in arable land. The methodology may also contribute certain indicators, for instance, on abatement requirements, which could serve as a complement to regulation and local quality measures on specific flows at an aggregated policy level. The stock perspective also sheds new light on actions such as increased recycling. Concerning the specific example used in the study, it is possible to achieve a future addition of cadmium in Swedish agricultural soils that is significantly lower than in the past, although the amount depends to a large degree on activities and policies outside Sweden. Considerable uncertainty exists regarding future depositions from air, especially that from distributed small‐scale emissions from fuel burning and reemission of already deposited cadmium from natural media. Measures must also be taken to guarantee a continued low addition in the form of mineral phosphorus fertilizers.

The possibility for energy regeneration by electrification in Swedish car driving

The ability to regenerate energy when braking is a valuable advantage of hybrid and fully electric vehicles. How much energy that can be regenerated depends mainly on the car driving and the capacity of the driveline. Detailed studies of possibilities for brake energy regeneration in real world driving are needed to better understand the potential gains of car-electrification since test cycles do not take individual driving or elevation into account. This study has analysed the potential for regeneration in Swedish car driving by applying a model for a normalized vehicle to a highly detailed and representative data set of individual car movements for privately driven cars in Sweden. The share of energy at the wheels used for braking was found to range from 12% to 63%, with an average of 30%. Engine braking could however reduce the amount of recoverable energy to about 16%. On average 42% and 89% of the potentially regenerable energy is available below 10 and 40 kW, respectively. Drivers with lower average speed have in general a higher share of the energy at the wheels potentially available for regeneration. This is however not an important factor to determine the total yearly energy/cost savings. Instead the yearly mileage is shown to be a more relevant indicator on total energy savings from regeneration. The results are compared to the NEDC and WLTP test cycles.

Dematerialization of the Metals Turnover

Relying on the characteristics of metals in society and nature, we have in this discussion on metals and dematerialization indicated that: A dematerialization of the societal metals turnover will mainly lessen the upstream problems connected to production of primary metals: the large rucksacks and the large indirect flows such as energy associated with mining and primary production of metals. A dematerialization will not be effective in mitigating many of the problematic downstream emissions originating in connection with specific application of the metals in various consumer goods. Here transmaterialization or substitution is a more viable strategy. The scarcity and by-flow characteristics of many metals may pose severe restrictions on the possible large-scale global application of many emerging and in other aspects environmentally benign technologies, especially in the energy sector. A dematerialization leading to an increased reliance on secondary instead of primary metals will require an increased focus on metals flow quality management to avoid down-cycling in the metals turnover.

A regionalized biophysically based model for the turnover of biomass and enteric methane emissions in the global food system

We have developed an extensive model for the turnover of biomass in the global food system. The turnover is driven by the (human) food intake and the necessary primary production above ground of major crops from arable land and pasture is calculated by an extensive physical modelling from harvest to food (energy and materials turnover). The model will be used to calculate the global emissions of methane from enteric fermentation, today, as well as under various possible scenarios for the agricultural sector. A preliminary estimate of the global methane emissions from enteric fermentation in domestic animals for the years 1992–94 is 110 Tg/y.