The effect of measurement time resolution on the peak time power demand reduction potential of domestic solar hot water systems

Autores:
Helena F. Naspolini, Ricardo Rüther
Evento:
Renewable Energy
Resumo:

The electrical resistance showerhead is the water heating technology used in over 70% of the Brazilian dwellings. These high power (5–8 kW are typical) instant heating devices contribute significantly to the demand peak in the early evening, and are a major burden to distribution utilities in Brazil. The objective of this paper is to define consumer showering patterns, and analyze the influence of the power demand measurement time resolution on the potential of peak time power demand reduction provided by Domestic Solar Hot Water (DSHW) systems. Results show that the measurement of electrical power demand in a 15-min interval is not adequate to evaluate and verify the benefits provided by the use of DSHW systems, because it heavily underestimates the active power demand reduction at peak hours. This work suggests that a 1-min time resolution can be considered appropriate to assess the potential impacts caused by the use of DSHW systems on the peak hours demand reduction.

Ano:

Simplified method for shading-loss analysis in BIPV systems. Part 2: Application in case studies

Autores:
Clarissa Zomer, Ricardo Rüther
Evento:
Energy and Buildings
Resumo:

This is the second part of the paper “Simplified method for shading-loss analysis in BIPV systems”. The objective of Part 2 is to apply the simplified method described in Part 1 in order to estimate the influence of partial shadings on the performance of four installed and in operation BIPV systems. The method consists in identifying and quantifying the shading on a surface, relating the fraction of shaded area with the percentage of incident irradiation reduction during the same period, in order to propose a shading index (SI) that represents the energy losses on partially shaded PV systems. SI was validated through the analysed case studies and it was proved to be a convenient way of estimating the PV generation of partially shaded PV systems. This method is independent from the electric configuration and can be used for already installed PV systems, or surfaces under investigation for PV installations, both through manual calculations and also through calculations using dedicated software packages.

Ano:

Energy performance evaluation of a net plus-energy residential building with grid-connected photovoltaic system in Brazil

Autores:
Giovani Almeida Dávi, Estefanía Caamaño-Martín, Ricardo Rüther, Juan Solano
Evento:
Energy and Buildings
Resumo:

The proposition of Net Plus-energy Buildings (NPEB) leads to the need to carry out studies of load matching in contrast with the grid impacts of distributed generation (DG). This paper performs simulations with the EnergyPlus software tool concerning a NPEB operating in four Brazilian metropolitan areas. The analyses include photovoltaic (PV) performance parameters and Load Matching and Grid Interaction indicators (LMGI). New grid impact indicators are defined in order to study the impacts of DG in the power grid. In the second stage, the work investigates economic aspects under net metering supporting. Results show the annual amount of electrical demand covered by PV varies from 29 to 51% with more potential in situations with higher PV production and higher cooling load, and the annual PV electricity that supplies the loads varies from 24 to 36% according to the seasonal variations of PV-load correlation. The levels of exported electricity into the grid are high in Brazil with annual mean power peaks surrounding 0.7 but can surpass 0.8 in the sunniest periods. The economy demonstrates the building achieves grid parity from 6 to 18% discount rates and the payback time is given for different scenarios of investment costs, discount rates and electricity tariffs.

Ano:

Simplified method for shading-loss analysis in BIPV systems. Part 2: Application in case studies

Autores:
ZOMER, CLARISSA ; Rüther, Ricardo
Evento:
Energy and buildings
Resumo:

This is the second part of the paper “Simplified method for shading-loss analysis in BIPV systems”. The objective of Part 2 is to apply the simplified method described in Part 1 in order to estimate the influence of partial shadings on the performance of four installed and in operation BIPV systems. The method consists in identifying and quantifying the shading on a surface, relating the fraction of shaded area with the percentage of incident irradiation reduction during the same period, in order to propose a shading index (SI) that represents the energy losses on partially shaded PV systems. SI was validated through the analysed case studies and it was proved to be a convenient way of estimating the PV generation of partially shaded PV systems. This method is independent from the electric configuration and can be used for already installed PV systems, or surfaces under investigation for PV installations, both through manual calculations and also through calculations using dedicated software packages.

Ano:

Simplified method for shading-loss analysis in BIPV systems - Part 1: Theoretical study

Autores:
ZOMER, CLARISSA ; Rüther, Ricardo
Evento:
Energy and buildings
Resumo:

This paper proposes a simplified method to determine an index to quantify the influence of partial shadings on the performance of BIPV systems based on the relation between the shading percentages and the reduction of the incident irradiation on a given surface. The research is divided in two papers: Part 1: Theoretical study and Part 2: Application in case studies. Part 1 consists in identifying and quantifying the shading on a surface, and relates the fraction of shaded area with the percentage of incident irradiation reduction during the same period, in order to propose a shading index (SI) that represents the energy losses due to shadings on PV systems. The method was developed for a theoretical shaded case study simulated in two cities located at low latitude, tropical regions: Singapore (1.35°N) and Florianópolis-Brazil (27.48°S). Results showed that the shading percentage on the analysed surface on an annual basis is closer to the percentage of incident irradiation reduction at same period than when these values are compared on other time bases, as hourly, daily or monthly. Therefore, in this case, the annual percentage of shading can be adopted as the SI. SI was validated using different computer software packages and it was proved to be a convenient way of estimation the PV generation of similar cases of partially shaded PV systems, that could be used even before the PV electrical desing has been done.

Ano:

Impacts of Domestic Solar Water Heating (DSWH) systems on the cost of a hot shower in low-income dwellings in Brazil

Autores:
Naspolini, Helena F. ; Rüther, Ricardo
Evento:
Renewable Energy
Resumo:

This work presents a method to evaluate, from the distribution utility's perspective, the impacts of adopting Domestic Solar Water Heating (DSWH) systems in Brazil, based on demand measurements carried out on two groups of residential households. For the 12 months period evaluated, the case-study shows that using DSWH results in savings of 198 kWh (38%), and active power demand savings at peak times of 860 W (42%) per individual unit. For the distribution utility and per individual unit, using DSWH leads to avoided costs of $ 27.59 (38%), avoided costs due to peak time demand reduction of $ 170.2 (42%), and annual avoided costs of $ 197.79 (41%). This work clearly shows that in the residential section the tariff model and structure is strongly distorted, since it only accounts for the energy consumption per residential unit, and completely disregards the costs associated with power demand availability. Our results show that in Brazil the distribution utility charges only some 15% of the real cost of a hot shower based on electric showerheads.

Ano:

The influence of different irradiation databases on the assessment of the return of capital invested in residential PV systems installed in different locations of the Brazilian territory.

Autores:
LACCHINI, CORRADO ; ANTONIOLLI, ANDRIGO FILIPPO ; Rüther, Ricardo
Evento:
Solar Energy
Resumo:

Rooftop residential photovoltaic (PV) generation is becoming more widespread among homeowners. A proper PV system design is crucial in order to avoid annual electricity production in excess of residential demand in countries where a net metering scheme is in place like in Brazil. It is therefore important that the information related to the average solar irradiation incident on the solar modules is accurately assessed, allowing precise estimates of photovoltaic electricity production. This work defines the criteria for the proper choice of a freely available irradiation database for the Brazilian territory and compares the results with the PVsyst-Meteonorm, a well-known modeling system. We demonstrate that, for Brazil, the Global Horizontal Irradiance (GHI) information provided by Openei-SWERA series is the best fit to different locations in the Brazilian territory, after introducing the corrections made by the horizontal to the plane-of-array transposition algorithms.

Ano:

Technical and economic evaluation of thin-film CdTe building-integrated photovoltaics (BIPV) replacing façade and rooftop materials in office buildings in a warm and sunny climate

Autores:
SORGATO, M.J. ; SCHNEIDER, K. ; Rüther, R.
Evento:
RENEWABLE ENERGY
Resumo:

A great challenge and trend for sustainable buildings is to reduce electricity consumption, and at the same time try to supply their own energy demand with self-generation. The project should be development focused on sustainability, explore the passive strategies and the energy generation potential of façades and roof. In this paper we analyze for the first time in Brazil and under current solar photovoltaic (PV) module prices, the technical and economic potential of integrating state-of-the-art, frameless, glass-glass thin-film cadmium telluride (CdTe) PV modules on a commercial building façade and roof, and evaluate the economic feasibility of replacing traditional façade materials like architectural glass and aluminum composite material with sleek black PV modules in six Brazilian cities. The technical analysis consisted in evaluating the energy performance of a four-storey office building for each of the six cities under analysis. The technical analysis showed that it is possible to fully meet the energy demand of the office building with PV integration in all the Brazilian cities evaluated. While the local climate has a significant impact on the energy consumption due mostly to air conditioning loads, PV energy production follows the same trend. Most importantly, the economic analysis showed that with the declining costs of photovoltaics, replacing conventional façade building materials with PV modules is not only an innovative approach but also of economic benefit.

Ano:

Towards the maximum efficiency design of a perovskite solar cell by material properties tuning: A multidimensional approach.

Autores:
KRATZENBERG, MANFRED G. ; Rüther, Ricardo ; RAMBO, CARLOS R.
Evento:
Solar Energy
Resumo:

To obtain significant increases in the Power Conversion Efficiency (PCE) of solar cells, we argue that the substitution of the state-of-the-art one- and two-dimensional cell optimizations, by the simultaneous improvement of multiple material properties is of substantial advantage. In this context, researchers should know, which combined material properties and cell design parameters result in the highest efficiency increase. For the same objective, it is also of importance to know, which ideal relationships in-between these variables have to be adjusted. Such knowledge becomes available by simulations and numerical optimizations, which we present for a Perovskite Solar Cell (PSC) in a hypercube space of model variables. We prove that its PCE increases principally because of the nonlinearities inherent to its mathematical model, and therefore, we elucidate the importance of the multidimensional variable improvements in the PSC’s optimization. We increased the PCE to a value of at least 27.6% by simultaneous improvements of the cell’s material properties, and light trapping, for a large range of absorber layer thicknesses, from t0 = 160 to 400 nm. The lower thickness results in a significant reduction of the device’s Pb content.

Ano:

Spectral modeling and spectral impacts on the performance of mc-Si and new generation CdTe photovoltaics in warm and sunny climates

Autores:
BRAGA, MARÍLIA ; DO NASCIMENTO, LUCAS RAFAEL ; Rüther, Ricardo
Evento:
Solar Energy
Resumo:

This paper presents an analysis of spectral impacts on mc-Si and new generation CdTe in two distinct regions of Brazil: Florianópolis-SC (27°S, 48°W) in the South, and Assu-RN (5°S, 37°W) in the Northeast. As utility-scale PV power plants are progressively being deployed in the Brazilian Northeast, the need for evaluation of the spectral effects of local blue-biased spectra on the energy yield of different PV technologies arises, as well as the need for spectral correction of field peak-power measurements done during commissioning and system performance tests. Considering the high cost of adequate spectral measurement equipment, this paper proposes a new approach for the estimation of spectral impacts without the need for in loco measurements. The proposed methodology consists of the use of satellite data acquired from NASA's Giovanni platform as inputs for the SMARTS 2.9.5 spectra model. Results for measured spectra showed that, for both locations, new generation CdTe (i.e. First Solar Series 4 and 6) has significant spectral gains: up to 10% for Assu-RN (Northeastern Brazil) and 2% for Florianópolis-SC (Southern Brazil). A seasonal variation could also be detected for the Florianópolis site, with lower spectral gains for CdTe - and higher for mc-Si - close to the Southern Hemisphere’s winter solstice, due to higher air mass values and lower precipitable water content of the atmosphere. The proposed method using Giovanni data and SMARTS spectra modeling produced very similar spectra to those measured for clear days in the field at both sites, yielding good results for the calculation of spectral factors for both mc-Si and CdTe. For days with a higher diffuse fraction the results were not as satisfactory, as expected. The proposed method was also applied to instantaneous measurements for three different times (and AM values) of the day for Florianópolis: 9:00, 12:00 and 15:00, yielding satisfactory results for IV curve spectral correction.

Ano:
Inscrever-se em