Solar Revolution - The Role of Photovoltaics for the Energy Transition
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The first part answers the question why there is a necessity for an energy transformation from fossil power generation to renewable energies in the first place. With a continuous increase in CO2-emissions and concentrations in the global atmosphere climate change will lead to an increase in global average temperature until the end of the century of approximately 4 - 5 degrees C. The costs of natural catastrophies thereby driven and intensified exceed the costs of such an energy transformation by a multitude. Instead of moaning about victims and persons affected, energy transformation has the potential to generate income and wealth for many.
Therefore, the second part deals with the question why there is an ongoing discussion in Germany about the concept and who is firing it. It identifies the losers and brakesmen of a changed political framework and portraits their motives to block and delay that change.
Hence, the third part puts emphasis on the special characteristics of photovoltaic energy generation and supply. It becomes clear that a consequent shift to 100 % renewable energies rather equals a revolution by literally empowering the people to become autonomous and self-sustaining. Trends in cost decrease and economy of scale give hope that this is only a matter of little time yet to come.
Conclusively, the fourth part gives an outlook into a future of 100% renewable energies and the technological and economical difficulties yet to overcome. This especially aims at the development and integration of storage capacity for electricity or its refragmentation and back-up in the form of Natural Gas.
This sums up to the conclusion that altogether energy transformation to a renewable energy system offers more chances and prosperity than business as usual.
Goals of a Sustainable Energy Development
The classical and superior triad of goals in energy policy consists of:
- security of energy supply
- cost effectiveness
- environmental sustainability
Thus, all forms of energy production and supply have to meet these goals. Renewable Energy Sources (RES) and given the topic of this particular lecture, Photovoltaics (PV) in particular are the only means of production and supply that achieve this. Especially when regarding electrical power, RES are the only technologies currently available and economically feasible.
Given the scientific undisputed fact of global warming or so-called climate change, RES are without alternative when it comes to mitigating climate change. Data, simulations as well as reports  confirm that there exists a rise in temperatures that is to a high probability caused by anthropogenic activity.
Winter storm "Xaver" in Germany and North-western Europe and typhoon "Hayan" in the Philippines are just the latest and most recent events in a serious of natural catastrophies increasing, both in magnitude and occurency. Since the year 2005 hurricane "Kathrina", 2005, a serious of Tornados in the Mid-West, 2012, hurricane "Sandy", 2010 and the two so-called centennial floods in Germany and neighbouring countries up- and downstream such as Switzerland, Austria, the Czech Republic, Poland and Slovenia have repeatedly raised concerns about the presence and outcome of climate change. Even more so, there is an ongoing discussion about the fatalistic drought in Eastern Africa, mainly on the territory of Somalia, Kenya, Athopia, Sudan and South Sudan to be one of the first natural catastrophies mainly induced and driven by climate change. 
Considering the current trend, global emissions continue to increase at present and in the near future and therewith, levels of CO2-concentration in the atmosphere. This is widely referred to as the "Business as usual"-scenario . Accordingly, until the end of the 21st century, CO2-concentration in the atmosphere according to this scenario leads to an increase in global average tmperature of at least 4 - 5C°, leaving the Arctic without ice coverage in summer months from ca. 2040 onwards.  These current and imminent developments support the urgency of a decarbonization of western, but also global economies and societies. In order to achieve this, it is self-evident to turn to RES as it is the most feasible, fast and cost effective path. Other strategies are less promising, as for instance, carbon trade up to this day proove.
In order to comply with a two-degree-increase-secenario, as suggested by the UN, IPCC and thus widely considered as a critical point for an "uncontrollable climate change" , it is indispensible to cut emissions of greenhouse-gases (GHG) by half globally by the year 2040.
Against this backgorund, the targets and resolutions of the german governments are not suitable or sufficient to reach zero-emissions by 2040. Statistics suggest that the major part of german reduction in GHG can be atttributed to the effect of German Reunion in 1989 and the resulting phaseout of former Eastern German heavy industry. Actually, GHG-emissions in Germany remain at a constant level.  In consideration of the steep increase of the share of RES in power production, the target marks of 40 - 45% until 2025, and 55 - 60% until 2035 respectively , can hardly be called ambitious and will easily be overachieved. Nevertheless, contradictions in german government's proclamation of CO2-reduction targets by 40% until the year 2040 remain. As that level of share of RES is not sufficient if electricity demand continues to steadily increase as it did so in the past.
Interstingly enough, politcal party affiliation did not have statistical significant influence on the character and speed of the annex of RES in recent years in Germany. Therefore, this is good reason to be convinced of the irresistible abiltity of RES to assert.
For a sustainable energy policy CO2-emissions have to be reduced to zero until 2040.
A wide mix of RES is able to achieve this.
Currently, politicians are not capable of introducing the necessary instruments for accelerating the pace in order to achieve this goal from top-down.
Loser and Brakesmen of a Fast Energy Transformation
Prejudices about the disadvantages of RES obstinately persist. Whereas the lignite-fired power plant in Jänschwalde may emit as much as three percent of german total CO2-emissions , this is not the only, even though most prominent negative environmental impact. Almost buried in oblivion today, coal mining and especially open-cast mining for lignite have tremendous and a vast variety of hazardous environmental effects. Among others ranks the detachment and emission of mercury in the process of allocation and combustion of fossil carbon. Round about 60% of all german mercury emissions originate from fossil coal-fired power plants . This quantity exceeds the amount of mercury that contain 240 000 000 energy-efficient lamps jointly. The most obvious effect of open-cast mining is the destruction of entire landscapes through the excavation of soil layers containing the fossil combustible, as subsequent damages in parts of Eastern Germany imposingly state, like in Lusatia and in the geographical region of Middle-Germany among others.
In comparison, environmental impacts of RES like windparks or open-field solar photovoltaic installations appear to be minor and only of temporary permanence. Nevertheless, arguments being brought forward, both by politicians and lobbyist do not correctly reflect this issue.
This also depicts the annex of electrical energy capacities in the current year 2013 in Germany. Whereas the annex of Photovoltaics diminished from recent record levels in 2011 and 2012 of ca. 7GW/a  to actual about 3GW in 2013, plans exist to build new carbon-fired power plants with an installed capacity of more than 3,4GWel . This thwarts German "Energiewende" and explains worries about the continuation and success of the concept.
This appears to be even more curious as the global trend seems to turn in the opposite direction. Germany, currently the biggest market of installed PV-capacity in the world, decided to cap PV-levies when total installed capacity reaches 52GWp . PV-installation capacities for China alone are projected to top the german numbers by late 2014 to mid-2015 , subsequently making it the leading market PV-market in the worled. A position the country and its PV-industry already undisbutedly hold for prodaction capacity and ratio. The current official chinese target corridor for the installed total PV-capacity in the year 2030 is between a lower value of 300 GWp and a higher value of 600 GWp. 
With regard to the portfolios of the four dominating market participants in Germany, RWE, Vattenfall, e.on and EnBW the lack of a significant share of RES in power production and supply is evident and remains well below 3% when excluding traditional renewable sources, i.e. Hydropower. This may surprise as the insight of RES as the only alternative in electrical power production finally makes its way to political top-level bodys.
A second frequent and predominant prejudice concerning RES, applies to their potential of power generation. The roof area in Germany alone adds up to ca. 1350 km² which corresponds to 161GWp  of potential PV-capacity and which is on a par to 0,4% of german territory. In comparison, current settlement- and traffic area in the year 2013 add up to more than 14% of german territory or 48 000km²  in total.
With less than 30GWp  installed in mid-2012 on a sunny Whitsun sunday PV generation in Germany provided up to 40% of the consumed electricity. This illustrates that with 70GWp, only twice the actual installed capacity of 35GWp, 100% renewable electrical supply already is close at hand.
Accordingly, fossil power plants and in particular carbon and nuclear power plants, because of their technolgoical restrictions do not qualify as so-called bridging-technologies into a renewable age. With the current installed PV-capacity of around 35GWp the projected tipping point of which path to choose of 50GWp is anything but far ahead.
The definetively most discussed prejudice against RES is the issue of cost-effectiveness and levelized costs of electricity (LCOE). In the period from the year 2000 - 2013 prices of electricity approximately doubled . 38% of this increase of 100% can be attributed to the RES-levy of the German EEG. The remaining 72% in price increase mainly arise from augmentation of prices of combustibles or other taxes and excise taxes. But what is generally overseen here is the point that this augmentation is well within the limits and trends of observed the inflatio-rate for that period of time. In fact prices of electricity at the European Energy Exchange (EEX) for retail costumers have begun to drop since the year 2008. This trend is ongoing today and is a direct consequence of the preference and zero marginal costs of electricity from RES, i.e. Wind and PV. Currently, the RES-levy for wind power is 8,93€ct/kWh. In comparison, Great Britain introduced a levy for electricity from Nuclear Power Plants of 11€ct/kWh with inflationary adjustment for 20 years. This example impressively adjusts the actual cost-effectiveness of electrical energy production. Even more so, it suggests the conclusion that costs and prices of electricity are anything but the decisive criteria. It seems quite obvious that rather politics and lobbying decide about energy policy and the technological path of the energy supply.
The traditional and dominating market players in electricity production and supply are trapped with unfit power production capacities for a changing energy framework and market environment. Attributing disproportionate LCOE to RES therefore serves as a means to the end of conserving their power and position by blocking the unlimited access of RES in the power and electricity market.
Decentralized Electricity for Citizens - Solar Revolution
China did not have any noteworthy installed PV-capacity in 2011. As mentioned above, in 2014 the country will be the leading market in PV installations. China is ambitious to achieve in only three years what took Germany more than a decade to realize. Regarding the consolidation, if not crisis on the global production market for PV wafers and modules, Germany runs the risk of losing touch with this hightech and future technology.
But not only the technology is innovative and new, so is the market and supply structure. Households and trade and commerce pay 28.9 €ct/kWh in average for electricity from the grid. PV is able to provide electrical energy according to cirumstances in between 7.8 to 14.2 €ct/kWh. This is more than grid-parity in Germany. This means that it already is economically benefitial for certain costumers to produce and consume their own electricity at the same time rather than obtaining electricity from the grid. This installation consumption is a specific characteristic of PV and will drive the demand for the technology as well as the development of the technology itself leading to a decentralized and autonomous energy supply structure.
Consequently, the future trend in photvoltaics and PV-systems is likely to be the integration of storage systems on a technical but rather economical level. PV wafer and module production has seen price reductions by economies of scale precedented by other semi-conductor devices before. The future task is to repeat this for battery technology as well. In Germany this system currently costs well below 1800 €/kWh for a short-term storage at good sites. With costs of 1250€/kWh for an installation of five kWp, the PV-system with storage then provides a Return on Investment (ROI) of 6%. This is equivalent to a cut in prices by a factor of four. In Germany the market volume is estimated to be 90GWp for this kind of installation. Other european markets appear to be attractive and lucrative as well. In the first place these are Spain, Portugal, Italy and Cypres.  Before this, in Germany PV will reach fuel-parity with oil in the year 2015 - 2016 and with Natural Gas in the year 2020 - 2022.
Beyond question in only a few years ahead LCOE of PV on the entire planet will be cheaper than those of a fossil electrical power supply. Structures of generation will swiftly democratise and installation consumption will be lucrative with or without any governmental guaranteed RES-levy.
A Safe Renewable Energy Supply
The German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), precisely the German Federal Environmental Minister, Peter Altmaier first aroused public awareness by the introduction of a concept of hedging LCOE, the so-called "Strompreisbremse". This paper introduces the idea of a EEG-solidarity tax because of the "increasing erosion of solidarity concerning the eeg-levy by costumer production and consumption".  This means a taxation of renewable electricity produced by independent and decentralized capacities in the hands of countless citizens.
In the same line stirs Jürgen R. Großmann when thinking abput a renewable energy system:"In january wind hardly blew and there was only littel sunshine. Imagine 80% of our electricity generation depending on RES. In times like these, not only lights would black out." 
Wind power and PV in the first place, but in general a mix of RES is mandatory when referring to a share of 80% of electricity production in 2040 and will guarantuee security of electricity production and supply. This requires an upgrade of electricity-grids. But other than pleaded by politics and influential think-tanks on the one hand this comes down to the enhancement of the distribution network at low voltage and not the installation of new maximum voltage supergrids.
When modelling and analysing a renweable energy system in Germany worst-case scenarios are decisive and critical for the success and feasibility of such a concept. Studies reveal that in that respect especially two cases turned out to be of special significance. 
Firstly, this is true for sunny spring-time periods, with moderate temperatures, likewise electricity demand and abundant wind yield and thus leading to extensive and relatively expensive power generation excesses. On the other hand therefore it is crucial to integrate sufficient short-term storage capacities and therewith shift renewable energy supply for some hours when demand starts to peak in the evening hours rather than transporting the electricity to distant regions in the moment of generation by new supergrids. Modells quantify this amount of storage capacity to approximately 400GWh of which 40 GWh are currently available yet. Presently those are pumped-storage hydro power plants predominantly.
Secondly, and finally the determining scenario is a winter-period with calm weather conditions characeterized by marginal sunshine and a neglegctable wind yield only. The main difference between this scenario and the first scenario is that necessary storage capacity in order to bridge slack periods must have long-term characteristics. As the next subsequent yield of wind or solar power is more uncertain und fluctuating than in spring-periods, energy supply has to be secured by sufficient retrievable back-up capacity. Currently research and development suggests that the infrastructure for Natural Gas widely fullfills the criteria therefore. Natural Gas is reformable throuh electrolysis by excess electric energy and is storageable with limited effort by existing infrastructure. Also there has been abundant experience for decades of dealing with that source of energy and its transformation into electric energy. The final storage capacity for Germany in a renewable energy system currently is estimated to about 30 TWh. The actual storage capacity for Natural Gas in Germany adds up to approximately 100 TWh.  This illustrates that technical potential and feasibility are already ensured.
An electric power generation and supply of 100% RES is realizable. In order to guarantuee 100% disposability and security of electric power supply Natural Gas storage capacity is essential. Consequently back-up power generation from Natural Gas is crucial and can be run by power-to-gas-methane. Storage for Natural Gas and batteries easily provide enough storage capacity.
The Energy Transformation (Energiewende) is a chance for Germany as a location for industry and high-tech. It serves as a link to modern trends and developments and helps to breed and to keep innovative ideas and evolutions, such as PV, fuel-cells, battery and power-to-gas technology in the country. Those are the exports of the future. There is no point in turning to expiring outdated engineering.
- It is climate change that determines the speed of energy transformation and demands a shift to 100% RES by the year 2040 in order not to run the risk of a "uncontrollable climate change" with an increase in global average temperatures well above two degrees.
- Politics and cooperations are not or hardly capable of inducing and managing that rapid change and are therewith not able to safe mankind's livelihood.
- Installation consumption will increase and soon become a leading driver for a democratisation of energy generation and supply as well as for a true energy revolution. There are 1.3 Mio PV-systems currently installed in Germany. The target number is projected to finally add up to tenfolds this quantity to 13 Mio installations in Germany alone.
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