Search

With increasing number of installations of photovoltaic (PV) systems and lower equipment costs, the subsidies dedicated to residential PV systems are reduced in many countries. Instead of the subsidies for selling PV electricity, prospectively self-consumption is the key parameter for the profitability of PV systems. In this paper, we study the market diffusion of residential PV systems for de-tached houses in Germany and Sweden. For this, we develop a hybrid model of the adoption of PV installations driven by self-consumption. We model the profitability and investment decisions for PV systems in a first step and account for inhibiting factors by introducing an adoption rate. The adoption rate is based on empirical data from the market diffusion of heat pumps in Sweden. We also study the market diffusion of battery systems aimed to increase self-consumption. A base case with several sensitivities on long-term trends of different parameters is analysed to examine the variation of the market diffusion until 2040. The results show a large difference in the market share of PV systems in Germany and Sweden in 2040. A base case scenario results in a market share for PV systems of 65% of the German detached houses in 2040, compared to 12% in Sweden. The results show that the market share in Sweden is most sensitive to electricity price changes, whereas the German market is most sensitive to changes in the adoption rate. Since the high electricity price in Germany makes PV profitable for most of the households at an early stage, it is mainly the adoption rate that limits the market diffusion in Germany. For Sweden, where the electricity price is less than half of the German price, the profitability is the main limiting factor. This is reflected in the hybrid adoption model, where the market diffusion is dependent on both the profitability and the adoption rate. The market share for battery systems is 5% in Germany and 0% in Sweden in 2040 in the base case scenario. The results show the influences of several parameters on the market diffusion based on the different initial mar-ket conditions, which can be extended to other national markets.

Worldwide installations of photovoltaics (PV) have increased rapidly due to national subsidies and decreasing prices. One important market segment is building-applied PV systems, for which the generated electricity can be self-consumed. Self-consumption is likely to become important both for the profitability and to facilitate integration of high shares of PV in the power system. The purpose of this doctoral thesis is to examine opportunities and challenges with distributed PV in the power system on four system levels: detached houses, communities, distribution systems and national level. This was done through literature studies and computer simulations. Previous research has shown a larger potential to increase the PV self-consumption in detached houses by using battery storage rather than shifting the household appliance loads. This thesis shows that, on the community level, the self-consumption increased more when sharing one large storage instead of individual storages in each house. On the distribution system level, PV power curtailment was identified as an effective solution to reduce the risk of overvoltage due to high PV penetration levels. However, the curtailment losses were high: up to 28% of the electricity production had to be curtailed in the studied distribution grid with a PV penetration of 100% of the yearly electricity consumption. However, the penetration of distributed PV on a national level is not likely to reach these levels. Around 12% of the Swedish households were estimated to have PV systems in 2040, although the uncertainties in the results were high, mainly related to the development of the electricity prices. The low profits from both PV but especially battery systems reduce future market shares. If residential batteries could also be used for primary frequency control, the profitability and thus the market shares for PV and battery systems could increase. The overall conclusions are that improved self-consumption can increase the profitability of PV systems and lower the negative impacts on grids with high PV penetration. Energy storage has a large potential to increase the self-consumption, but the profitability is still low for a storage that is only used to increase the self-consumption.

Renewable distributed generation and electric vehicles (EVs) are two important components in the transitions to a more sustainable society. However, both distributed generation and EV charging pose new challenges to the power system due to intermittent generation and high-power EV charging. In this case study, a power system consisting of a low- and medium-voltage distribution grid with more than 5000 customers, high penetration of roof-top mounted photovoltaic (PV) power systems and a fully electrified car fleet is used to assess the impact of the intermittent PV generation and high-power EV charging loads. Two summer weeks and two winter weeks with and without EV charging and a PV penetration varying between 0% and 100% of the annual electricity consumption are examined using measured and simulated data. Results show that the electricity consumption increases with 9% and 18% during the studied periods, and that EV charging only marginally can contribute to lowering the risk of overvoltage for customers resulting from PV overproduction. The most significant result is the increase in undervoltage in the winter when EV charging is introduced. The share of customers affected by undervoltage increases from 0% to close to 1.5% for all PV penetration levels.

The global market for photovoltaics (PV) has increased rapidly: during 2014, 44 times more was installed than in 2004, partly due to a price reduction of 60-70% during the same time period. Economic support schemes that were needed to make PV competitive on the electricity market have gradually decreased and self-consumption of PV electricity is becoming more interesting internationally from an economic perspective. This licentiate thesis investigates self-consumption of residential PV electricity and how more PV power can be allowed in and injected into a distribution grid. A model was developed for PV panels in various orientations and showed a better relative load matching with east-west-oriented compared to south-oriented PV panels. However, the yearly electricity production for the east-west-system decreased, which resulted in less self-consumed electricity. Alternatives for self-consumption of PV electricity and reduced feed-in power in a community of detached houses were investigated. The self-consumption increased more with shared batteries than with individual batteries with identical total storage capacity. A 50% reduction in feed-in power leads to losses below 10% due to PV power curtailment. Methodologies for overvoltage prevention in a distribution grid with a high share of PV power production were developed. Simulations with a case with 42% of the yearly electricity demand from PV showed promising results for preventing overvoltage using centralized battery storage and PV power curtailment. These results show potential for increasing the self-consumption of residential PV electricity with storage and to reduce stress on a distribution grid with storage and power curtailment. Increased self-consumption with storage is however not profitable in Sweden today, and 42% of the electricity from PV is far more than the actual contribution of 0.06% to the total electricity production in Sweden in 2014.

Most of the photovoltaic (solar cell) systems in Sweden today are installed on private houses and connected to the public grid. Photovoltaic (PV) power can be consumed directly in the house, called self-consumption, or fed in to the public grid. For the house owner self-consumed PV energy often has a higher economic value than sold excess PV energy, since the savings from not buying one kWh is larger than the income of selling one kWh. The self-consumption can be expressed as an absolute value; amount of produced/consumed kWh, or as a relative; absolute self-consumption divided with total PV production. The PV production and self-consumption were calculated on an hourly basis. In this Master thesis a MATLAB tool for calculating and optimizing the production, absolute and relative self-consumption and profit for PV systems with panels in one (1DPV), two or three directions (3DPV) was developed. The results show possibilities to increase especially the relative self-consumption with 3DPV. There is however no economic gain of using 3DPV instead of south-directed 1DPV for the studied case; a private house close to Västerås with a 1DPV system of 3360 W and variable electricity prices based on hourly Nord Pool Spot prices. The rated power of the inverter can be decreased with 3DPV compared to south-oriented 1DPV and still keep minimal production losses. A smaller inverter and other peripheral equipment such as cables might compensate for the lower yearly profit with 3DPV when calculating the payback period. Further studies of economic aspects and how to optimize them have to be carried out for 3DPV systems, since economy is very crucial for investment decisions.