4 research outputs found
Ultra-Low Power Transmitter and Power Management for Internet-of-Things Devices
Two of the most critical components in an Internet-of-Things (IoT) sensing and transmitting node are the power management unit (PMU) and the wireless transmitter (Tx). The desire for longer intervals between battery replacements or a completely self-contained, battery-less operation via energy harvesting transducers and circuits in IoT nodes demands highly efficient integrated circuits. This dissertation addresses the challenge of designing and implementing power management and Tx circuits with ultra-low power consumption to enable such efficient operation.
The first part of the dissertation focuses on the study and design of power management circuits for IoT nodes. This opening portion elaborates on two different areas of the power management field: Firstly, a low-complexity, SPICE-based model for general low dropout (LDO) regulators is demonstrated. The model aims to reduce the stress and computation times in the final stages of simulation and verification of Systems-on-Chip (SoC), including IoT nodes, that employ large numbers of LDOs. Secondly, the implementation of an efficient PMU for an energy harvesting system based on a thermoelectric generator transducer is discussed. The PMU includes a first-in-its-class LDO with programmable supply noise rejection for localized improvement in the suppression.
The second part of the dissertation addresses the challenge of designing an ultra-
low power wireless FSK Tx in the 900 MHz ISM band. To reduce the power consumption and boost the Tx energy efficiency, a novel delay cell exploiting current reuse is used in a ring-oscillator employed as the local oscillator generator scheme. In combination with an edge-combiner PA, the Tx showed a measured energy efficiency of 0.2 nJ/bit and a normalized energy efficiency of 3.1 nJ/(bit∙mW) when operating at output power levels up to -10 dBm and data rates of 3 Mbps. To close this dissertation, the implementation of a supply-noise tolerant BiCMOS ring-oscillator is discussed. The combination of a passive, high-pass feedforward path from the supply to critical nodes in the selected delay cell and a low cost LDO allow the oscillator to exhibit power supply noise rejection levels better than –33 dB in experimental results
Integration of the German energy transition in the EU-context
The reduction targets of carbon dioxide emissions are set on EU and national level. However the transition process towards such a low carbon society is characterised by a high degree of uncertainty and complexity. Thus possible strategies and measures need to be able to adjust to uncertain changes, overcome stagnations due to conflicts and foster innovations. The most important prerequisite to accomplish effective and efficient measures towards a low carbon society is to produce robust knowledge. The production of robust and applicable knowledge is based on an interdisciplinary approach that considers the multi-dimensional and vale-based concept of sustainability. Meaning that the integration of the different knowledge types system knowledge, target knowledge and transformations knowledge is a core challenge of developing sustainable solution. In this manner the Institute of Energy and Climate Research – Systems Analysis and Technology Evaluation (IEK-STE) operationalises and investigates social and political principles and objectives in terms of their importance for future energy systems and the associated transformation process. The R&Dialogue project contributed to this aim in testing a new approach of knowledge co-production and fostering the dialogue between science and civil society. ..
Benchmarking renewable energy sources carbon savings and economic effectiveness
Over the last decade, the levelised cost of energy (LCOE) of many renewable technologies
has sharply declined. As a result, direct cost comparisons of LCOE figures have made
renewables to be perceived as economically very competitive options to decarbonise energy
systems when compared to other low-carbon technologies such as Nuclear and Carbon
Capture and Storage. We identify several theoretical shortcomings in relation to using LCOE
or similar life-cycle economic metrics to make inferences about the relative economic
effectiveness of using renewable technologies to decarbonise energy systems. We outline
several circumstances in which the sole reliance on these metrics can lead to suboptimal or
misguided investment and policymaking decisions.
The thesis proposes a new theoretical framework to measure and benchmark the cost-
effectiveness of decarbonising electric systems using renewables. The new framework is
generic, technology-neutral, and enables consolidation of the results of decarbonisation
studies that consider various renewable technologies and low carbon technologies. It also
enables measuring and tracking the cost-effectiveness of the renewable decarbonisation
process at a country or a system level. As a result, it also allows the direct comparison of the
economic implications of different decarbonisation scenarios and various policy proposals in
a very intuitive graphical way.
In addition, the thesis proposes a new, unit-free metric, tentatively called Carbon Economic
Effectiveness Credit (CEEC), to benchmark the relative cost-effectiveness of using different
renewable technologies to achieve long-term carbon emission savings. Theoretically, CEEC
represents the elasticity of the system total cost with respect to the carbon reduction savings
attributable to renewables. In contrast to stand-alone, life-cycle metrics such as the LCOE,
the proposed metric considers the economic and technical parameters of the renewable
technologies and characteristic of the system under study. It also allows expressing the cost-
effectiveness of the renewable decarbonisation process as a function of the system-wide
decarbonisation level.
Using historical load profiles, high-resolution solar radiation data and long-term
meteorological data for a relatively small Gulf country, we investigate the deep
decarbonisation of the electric system through the large-scale deployment of different
renewables technologies. In particular, we use two well-established optimisation methodologies that have been used extensively in the literature to study the decarbonisation
of power systems, namely: the screening curve (SC) method and the unit commitment (UC)
method. In analysing the results of the two methodologies, we find that the choice of the
modelling methodology, in some cases, can greatly influence the perceived carbon cost-
effectiveness of renewables and subsequently their carbon abatement cost estimates. In
particular, our results suggest that under deep decarbonisation scenarios, the estimate of the
long-term carbon savings of renewables is strongly influenced by (1) the choice of the
modelling method and (2) the technical specifications of the simulation models. Our results
suggest that under deep decarbonisation scenarios, using simpler optimisation models
may change the perceived economic effectiveness of renewables to decarbonise some
electric systems. More importantly, our research sheds light on potential shortcomings in the
current modelling practices and help identify patterns of possible inaccuracies or biases in
renewable decarbonisation results.
Moreover, our research suggests that the variations in the technical characteristics of
renewable technologies can have a large influence on the economics of the decarbonisation
process. We show that not all renewable technology types can have a suppressing effect on
the variable costs of the systems due to their “zero marginal costs.” In particular, we identify
certain technologies and circumstances in which an increase in renewable penetration can
significantly inflate the variable energy costs of the system. More specifically, we find that
under deep decarbonisation scenarios, renewable technologies with a highly volatile
production profiles can act as an amplifier for the variable cost of the systems through (1)
reducing the effectiveness of thermal generation units due the increased start-up and
shutting downing activities, and (2) increasing the energy output levels from more flexible
and yet more expensive thermal technologies.
In addition, we identify circumstances in which an increased renewable penetration can
materially affect the capacity adequacy of electric systems, leading to an increase in capacity
investment in thermal flexibility assets. Perhaps more importantly, we find that these
additional flexibility assets will not be commercially viable on an energy-output basis. We
believe that this might have specific implications for the energy-only markets.
Finally, we discuss the policy implications of our findings and propose several important
recommendations. Altogether, we hope that our work will advance the understanding of the
economics of climate change and integrating renewables into energy systems.Open Acces