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Due to advances in computing and modeling, the Architecture Engineering and Construction (AEC) industry has arrived at an era of digital empiricism. Computational simulation tools are widely used across many engineering disciplines for design, evaluation and analysis. Experts in the field agree thatdesign decisions taken during the early design stages have a significant impact on the real performance of the building. Nevertheless, building performance simulation is still hardly used during conceptual design. The European Commission has targeted a 20% reduction of CO2 emissions, a 20% increase of energy efficiency and a 20% increase in the use of renewable energy by 2020. These ambitious aims have resulted in the recasting of the Energy for Buildings Directive, demanding nearly-zero-netenergy- buildings for new buildings and major refurbishments by 2020. The formulated aim requires for the first time an integrated design of the building’s demand and supply systems. The current research was triggered by the above observation. It uses semi-structured interviews and critical reviews of literature and software to establish the reasons that prevent Heating, Ventilation and Air Conditioning (HVAC) consultants from adopting Building Performance Simulation (BPS) tools and to identify the needs of practitioners during the conceptual design stage. In response to the identified needs, a rapid iterative development process is deployed to produce a prototypical software tool. Finally, the tool is heuristically tested on expert users to evaluate its capability to support the conceptual design process. The results obtained from interviews and reviews highlight that HVAC consultants work with an increasing number of design alternatives to prevent dysfunctional buildings. The complexity of design problems is increasing on the one hand due to the need for an early integration of engineering discipline’s and on the other hand due to the challenges in meeting the even more stringent requirements of new buildings. Furthermore, design teams run the risk of only identifying suboptimal solutions for the design problem when they limit themselves too early to a small number of design alternatives. The use of simulation tools helps facilitate a quick turnaround of performance evaluations for a great number of design alternatives early in the design process. By doing so, performance simulation tools have the potential to supplement design experience and support decision making. However, simulation tools are perceived by many as too detailed to be readily used for conceptual design support. Research findings suggest that tools for the early design stages are required to enable parametric studies and to provide facilities to explore the relationships between potential design decisions and performance aspects. Tools need to be able to dynamically scale the resolution of their interfaces to fit the different levels of information density characteristic of the different design stages. In addition, they need to be flexible enough to facilitate expansion of the system representations with innovative design concepts as the design progresses. Due to the need for parametric studies and the exploration of the relationships between potential design decision and performance aspects, this research explores the extension and application of BPS tools with techniques for uncertainty propagation and sensitivity analysis for conceptual design support. This endeavor requires (1) the evaluation and selection of an extension strategy, (2) the determination of the format and availability of input to techniques for uncertainty propagation and sensitivity analysis, as well as (3) developing knowledge regarding the extent and content of the design option space. To avoid the need to modify the source code of BPS tools, an external strategy is applied that embeds an existing simulation engine into a shell with extra features for statistical pre and post-processing by Latin Hypercube sampling and regression based sensitivity analysis. With regards to the model resolution, results suggest that it is more beneficial to use detailed models with adaptive interfaces rather than simpler tools. The advantages are twofold. Firstly, the BPS tool can use an existing validated simulation model - rather than a specifically developed abstract model with limited applicability. Secondly, the model is able to provide consistent feedback throughout the lifetime of the building. Within the iterative process, the conceptual design stage has some distinctive tasks, such as to explore the option space and to generate and evaluate design concepts. The option space is multidimensional, due to its multi-disciplinary set-up and wide-ranging interests of the participating practitioners. An empirical study as part of the research demonstrates the presence of at least two attributes, four subsystem categories and four relationships. Depending on the experience of the practicing designer, components, attributes and relationships are used to a very different extent. While experienced HVAC consultants seem to work mainly with relationships when compiling a design concept, novice designers prefer to work with components. The sampling based analysis strategy requires knowledge about the uncertainty of the parametric model input in the form of probability distribution functions. On the basis of a survey on internal gains for offices, this thesis concludes that current design guidelines provide useful data in a suitable format. Measurements conducted in an office building in Amsterdam confirm the trend towards decreasing equipment gains and the proportional increase of lighting gains. However, in the absence of data to derive a probability density function, this research suggests the definition of "explanatory" scenarios. It is common practice to use "normative" scenarios as input in building performance studies aiming to prove compliance with building regulations. The use of "exploratory" scenarios is less common. Scenario based load profiles have to meet three characteristics. They have to be: (1) locally representative; (2) up-to date and (3) need to match workplace culture. As part of this thesis explanatory data sets were developed representing climate change scenarios for The Netherlands. The exploratory scenarios facilitate the robustness assessment of the future performance of design alternatives. Tests with the Dutch data sets confirm that neither the current reference data nor the projected reference data provide valid results to predict uncertainty ranges for the peak cooling load as a potential robustness indicator. A simulation based comparative robustness assessment of three HVAC concepts over 15 and 30 years is reported. The results indicate a robust future performance for the floor-cooling based design alternative with respect to thermal comfort and cooling energy demand. The software prototype shows that detailed simulation tools with features for uncertainty propagation and sensitivity analysis provide the facilities to explore consequences of potential design decisions on performance aspects. In addition, they enable parametric studies and create the possibility to quantify parameter interactions and their collective impact on the performance aspect. Heuristic usability evaluation of the software prototype confirms the value to design practice. 85% of approached HVAC consultants state that the uncertainty of performance aspects is an important parameter to support conceptual design. More importantly, 80% of the practitioners consider the prototype to have great potential to reduce the number of necessary design iterations. This thesis concludes that simulation tools that quantitatively address uncertainties and sensitivities related to conceptual building design generate value by (1) providing an indication of the accuracy of the performance predictions; (2) allowing the identification of parameters and systems to which performance metrics react sensitively and in-sensitively, respectively; and (3) enabling a robustness assessment of design alternatives.

Solar cells convert solar energy directly into electricity and are attractive contribute to the increasing energy demand of modern society. Commercial mono-crystalline silicon based devices are infiltrating the energy market but their expensive, time and energy consuming production process necessitates alternative semiconductor materials. Recently advances in the field of polymer based solar cells have resulted in devices that feature power conversion efficiencies over 7% which approaches the threshold for successful commercialization. A fundamental tradeoff between current and voltage limits the ultimate power conversion efficiency in single junction solar cells because photons with energies larger than the band gap will lose their excess energy via thermal equilibration and photons with energies smaller than the band gap cannot be absorbed. In a tandem solar cell, a wide band gap subcell will reduce the thermalization losses of high energy photons and a small band gap subcell will lower the transmission losses of low energy photons. For efficient operation of the tandem, these subcells must be combined via a transparent intermediate contact consisting of an electron and hole transporting layer that enables a good physical separation of the two photoactive layers and a good electrical connection without voltage loss. This thesis aims to fabricate, optimize, and characterize polymer tandem solar cells with all layers processed from solution. Solution based techniques (e.g. printing) are commercially more interesting than evaporation or sputter steps in vacuum because these techniques are less time and energy consuming and eventually allow for high speed roll-to-roll production. The main challenge is to find materials that possess optimized optical and electronic properties for efficient operation and that can be processed into thin multilayer stacks from solution in such a way that each successive layer is deposited without disrupting the integrity of underlying layers. As a first step towards polymer tandem solar cells a transparent electron transporting layer has been developed that can be processed from solution (Chapter 2). It was found that a ZnO layer, deposited in the form of nanoparticles from acetone, can be employed. ZnO fulfills all requirements for an electron transporting layer and acetone is one of the few solvents that is innocuous to the underlying active layer and provides sufficient wetting to enable the formation of thin, closed, and transparent layers. Incorporating a ZnO layer in solar cells between the active layer and the reflective electrode led to working devices for active layers consisting of various polymers mixed with a fullerene derivative. In fact, insertion of the thin ZnO layer even led to an improved current density. Optical modeling showed that this beneficial effect can be attributed to a redistribution of the optical electric field inside the device that shifts the position of the maximum optical field into the active layer and increases the absorption of light. ZnO works as an optical spacer. This is especially interesting for polymer solar cells where the optimal layer thickness is limited by to a low charge carrier mobility. For the completion of the recombination layer, a hole transporting layer is needed. Because of its acidic nature, the commonly used PEDOT:PSS dispersion is detrimental for the ZnO layer. In Chapter 3 it is shown, however, that a pH neutral PEDOT can be used successfully as a hole transporting layer to fabricate solution processed polymer multiple junction solar cells. Contact problems at the ZnO/pH neutral PEDOT interface were resolved by photodoping of the ZnO layer. This increases the concentration of mobile electrons in the ZnO and creates an Ohmic contact between ZnO and pH neutral PEDOT. The open-circuit voltage of multiple junction solar cells increased from 1.57 to 2.19 and 3.58 V for two, three and six active layers. To make an efficient tandem cell, efficient wide and small band gap subcells must be combined. Chapter 4 describes the optimization of a small band gap cell based in a novel alternating copolymer of diketopyrrolopyrrole and quarterthiophene units. The morphology of the active layer and the performance of the solar cell were optimized by varying the processing conditions. Power conversion efficiencies of 3.6% and 4.0% were obtained in combination with C60 and C70 derivatives as acceptors by processing from a mixed chloroform/o-dichlorobenzene solution to ensure the correct balance between solubility and aggregation of polymer chains. In Chapter 5 it is demonstrated how a combined analysis of the optical absorption and electrical characteristics of the individual wide and small band gap single junction subcells can be used to identify the optimum device layout of the corresponding tandem cell. In contrast to existing views, matching the photocurrents of the subcells is not the best criterion for optimum performance, because the short-circuit current of a polymer tandem cell can exceed that of the current-limiting subcell. Using the new methodology, a solution processed polymer tandem cell with a power conversion efficiency of 4.9% was made, higher than the efficiency of the optimized single layer devices. This experimental result agrees well with the predicted value, indicating that this technique represents a universal method to improve the efficiency of future tandem solar cells. The current density generating capacities of the subcells were unmatched proving that the current-limiting subcell can be assisted by the other subcell in a polymer tandem solar cell. The strong optical and electrical interplay of the two subcells has important consequences for the accurate characterization of the tandem cell, especially with respect to measuring the external quantum efficiency. Chapter 6 describes a new procedure to accurately characterize two-terminal polymer tandem solar cells. The spectral response measurement of polymer tandem solar cells is complicated by sub-linear light intensity dependence and field-assisted current generation, requiring the use of an optical and an electrical bias. The required magnitude of optical and electrical biases was determined using single junction "dummy" cells, identical to the tandem subcell, and by determining the absorption spectra of the active layers in the stack obtained via optical modeling. Finally, the current density to voltage characteristics of the subcells of polymer tandem solar cells—permitting a better understanding of the functioning of the tandem cell—has been explored via two techniques (Chapter 7). First, an auxiliary electrode in between the electron and hole transporting layer but situated just outside of the photoactive area enabled making a three-terminal device structure without disturbing the optical electric field in the stack. This auxiliary electrode can be used for determining the bias offset between the recombination layer and either terminal electrode to provide the subcell characteristics. As an alternative method, an electrical bias sweep in the spectral response measurement of the subcells results in the current density to voltage curves of the subcells after convolution of the spectral response with the AM1.5G solar spectrum. The results of the different methods were verified and validated by cross-checking. In conclusion, the research described in the thesis has established new methods for fabricating, optimizing, and characterizing polymer tandem solar cells that can be processed from solution. The methods that have been developed are general and can be used to manufacture efficient tandem structures based on a detailed knowledge of the characteristics of single junction cells. Combined with the recent advances in the efficiency of organic solar cells based on new materials, the prospects for efficient polymer tandem solar cells are excellent.

During the past decade, electrical power systems have been going through some major restructuring processes. From monopolistic, highly regulated and one utility controlled operation, a system is being restructured to include many parties competing for energy production and consumption, and for provision of many of the ancillary services necessary for system operation. With the emergence of competitive markets as central operational mechanisms, the prime operational objective has shifted from a centralized, utility cost minimization objective to decentralized, profit maximization objectives of competing parties. The market-based (price-based) operation is shown to be practically the only approach that is capable to simultaneously provide incentives to hold the prices at marginal costs and to minimize the costs. As a result, such an operational structure inherently tends to maximize the social welfare of the system during its operation, and to accelerate developments and applications of new technologies. Another major change that is taking place in today’s power systems is an increasing integration of small-scale distributed generation (DG) units. Since in future power systems, a large amounts of DG will be based on renewable, intermittent energy sources, e.g. wind and sun, these systems will be characterized by significantly larger uncertainties than those of the present power systems. Power markets significantly deviate from standard economics since the demand side is largely disconnected from the market, i.e. it is not price responsive, and it exhibits uncertain, stochastic behavior. Furthermore, since electrical energy cannot be efficiently stored in large quantities, production has to meet these rapidly changing demands in real-time. In future power systems, efficient real-time power balancing schemes will become crucial and even more challenging due to the significant increase of uncertainties by large-scale integration of renewable sources. Physical and security limits on the maximal power flows in the lines of power transmission networks represent crucial system constraints, which must be satisfied to protect the integrity of the system. Creating an efficient congestion management scheme for dealing with these constraints is one of the toughest problems in the electricity market design, as the line power flows are characterized by complex dependencies on nodal power injections. Efficient congestion control has to account for those limits by adequately transforming them into market signals, i.e. into electricity prices. One of the main contributions of this thesis is the development of a novel dynamic, distributed feedback control scheme for optimal real-time update of electricity prices. The developed controller (which is called the KKT controller in the thesis) reacts on the network frequency deviation as a measure of power imbalance in the system and on measured violations of line flow limits in a transmission network. The output of the controller is a vector of nodal prices. Each producer/consumer in the system is allowed to autonomously react on the announced price by adjusting its production/consumption level to maximize its own benefit. Under the hypothesis of global asymptotic stability of the closed-loop system, the developed control scheme is proven to continuously balance the system by driving it towards the equilibrium where the transmission power flow constraints are satisfied, and where the total social welfare of the system is maximized. One of the advantageous features of the developed control scheme is that, to achieve this goal, it requires no knowledge of marginal cost/benefit functions of producers/consumers in the system (neither is it based on the estimates of those functions). The only system parameters that are explicitly included in the control law are the transmission network parameters, i.e. network topology and line impedances. Furthermore, the developed control law can be implemented in a distributed fashion. More precisely, it can be implemented through a set of nodal controllers, where one nodal controller (NC) is assigned to each node in the network. Each NC acts only on locally available information, i.e. on the measurements from the corresponding node and on the information obtained from NC’s of the adjacent nodes. The communication network graph among NC’s is therefore the same as the graph of the underlying physical network. Any change is the network topology requires only simple adjustments in NC’s that are local to the location of the change. To impose the hard constraints on the level to which the transmission network lines are overloaded during the transient periods following relatively large power imbalances in the system, a novel price-based hybrid model predictive control (MPC) scheme has been developed. The MPC control action adds corrective signals to the output of the KKT controller, i.e. to the nodal prices, and acts only when the predictions indicate that the imposed hard constraint will be violated. In any other case, output of the MPC controller is zero and only the KKT controller is active. Under certain hypothesis, recursive feasibility and asymptotic stability of the closed-loop system with the hybrid MPC controller are proven. Next contribution of this thesis is formulation of the autonomous power networks concept as a multilayered operational structure of future power systems, which allows for efficient large-scale integration of DG and smallscale consumers into power and ancillary service markets, i.e. markets for different classes of reserve capacities. An autonomous power network (AN) is an aggregation of networked producers and consumers, whose operation is coordinated/controlled with one central unit (AN market agent). By performing optimal dispatching and unit commitment services, the main goals of an AN market agent is to efficiently deploy the AN’s internal resources by its active involvement in power and ancillary service markets, and to optimally account for the local reliability needs. An autonomous power network is further defined as a major building block of power system operation, which is capable of keeping track of its contribution to the uncertainty in the overall system, and is capable of bearing the responsibility for it. With the introduction of such entities, the conditions are created that allow for the emergence of novel, competitive ancillary service market structures. More precisely, in ANs based power systems, each AN can be both producer and consumer of ancillary services, and ancillary service markets are characterized by double-sided competition, what is in contrast to today’s single-sided ancillary service markets. One of the main implications of this novel operational structure in that, by facilitating competition, it creates the strong incentive for ANs to reduce the uncertainties and to increase reliability of the system. On a more technical side, the AN concept is seen as decentralization and modularization approach for dealing with the future, large scale, complex power systems. As additional contribution of this thesis, motivated by the KKT controller for price-based real-time power balancing and congestion management, the general KKT control paradigm is presented in some detail. The developed control design procedure presents a solution to the problem of regulating a general linear time-invariant dynamical system to a time-varying economically optimal operating point. The system is characterized with a set of exogenous inputs as an abstraction of time-varying loads and disturbances. Economic optimality is defined through a constrained convex optimization problem with a set of system states as decision variables, and with the values of exogenous inputs as parameters in the optimization problem. A KKT controller belongs to a class of dynamic complementarity systems, which has been recently introduced and which has, due to its wide applicability and specific structural properties, gained a significant attention in systems and control community. The results of this thesis add to the list of applications of complementarity systems in control.