Analytical Model for the Performance of a Free-Space Luminescent Solar Concentrator

Conventional luminescent solar concentrators suffer from high losses due to the large path length inside the device. Our system reduces these losses by using the free-space to collimate the light. We have developed an analytical model for the performance of those free-space luminescent solar concentrators. Our model takes all loss mechanisms into account and outputs the angle and wavelength dependent emission. Using realistic material parameters, we calculate the intensity emitted by the free space concentrator to be 1.5 times higher than that of a perfect diffuse reflector for all emission angles below 19 degrees

Free-Space Diffused Light Collimation and Concentration

Collimating and concentrating broad-band diffused light can increase the yield, decrease the cost, and open new opportunities for solar-generated electricity. Adherence to the second law of thermodynamics requires that collimation, and therefore the reduction of étendue or entropy, of diffused sunlight, i.e., light scattered by clouds or the atmosphere, can only occur if the photons lose energy during the process. This principle has been demonstrated in luminescent solar concentrators; solar photons are energetically down-shifted by a luminophore and the emitted photons are trapped within a transparent matrix and guided toward an edge lining solar cell. However, this process suffers from low efficiency as the photons are trapped within the waveguide for a long time, encountering many instances of accumulating loss mechanisms. Here, we theoretically describe and experimentally demonstrate the first free-space diffused light collimation system which overcomes these efficiency losses. The high photon energy solar spectrum is allowed to enter the system from all angles, whereas the re-emitted luminescent photons can only escape under a desired emission cone. We achieved this through doping a polymethylmetacrylate waveguide with Lumogen Red dye, which we cover on one side with a Lambertian reflector for photon recycling and induced randomization and on the top face with a complex multilayer dielectric nanophotonic coating stack. We experimentally found an angular concentration of 118% within the designed escape cone, where isotropic emission corresponds to 100%, thereby verifying the reduction of étendue in free space experimentally. Such free-space collimation systems will enable efficient redirection of sunlight toward solar panels, thereby increasing yield, decreasing heating through the emission of low energy photons, and expanding the range of available surfaces from which sunlight can be harvested

International Social Survey Programme: Citizenship - ISSP 2004

Citizen and state. Topics: Qualities of a good citizen; attitude toward the right ofpublic meetings for religious extremists, people who want to overthrowthe government by force, or people prejudiced against any racial orethnic group; social and political participation; memberships;importance of different people`s rights in democracy (scale);estimation of political influence possibilities (political efficacy);likeliness of counter-action against an unjust law and expected chanceof serious attention to people`s demand; interest in politics; personaltrust in politicians and people; political discussions with friends;opinion leadership in politics; national sovereignty and attitude tointernational organisations; attitude to the action of politicalparties; real policy choice between parties; attitude toward areferendum; level of honesty and fairness in the last nationalelection; commitment to serve people and likeliness to correct ownmistakes in public service; corruption in public service; functioningof democracy at present, in the past and in the future; frequencies ofmedia use; respect for people and tolerance in case of disagreement;self-description of the habitation (residence); voter participation;voting behaviour (recall). Demography: Sex; age; marital-status; steady life-partner; education;current employment status; hours worked weekly; occupation (ISCO 1988);working for private or public sector or selfemployed; if selfemployed:number of employees; supervisor function; trade union membership;current employment status (ISCO 1988); earnings; family income;household size; household composition; party affiliation; participationin last election; religious denomination; attendance of religiousservices; self-placement on a top-bottom scale; region; size ofcommunity; type of community: urban-rural area; ethnicity, nationalityand family-origin. Additionally coded: administrative mode of data-collection