تجزیه و تحلیل هزینه چرخه عمر خانه غیرفعال "POLITEHNICA" از بخارست

The objective of this article is to create a mathematical model based on the analysis of the life cycle cost of a passive house, including its technical design variations. In this study we analyzed 14 types of houses derived from the design of the passive house POLITEHNICA; every house was differentiated by the type of renewable solution used (EAHX, GHP, solar collectors, PV panels) or by the insulation thickness, and it was compared with H12, a standard house with classical HVAC systems and a thermal insulation of 100 mm. The houses were compared according to criteria of economic performance throughtout their life cycle. It was found that the additional investment in an energy efficient house can be recovered in 16-26 years, 9-16 years and 16-28 years if the replaced HVAC system is classical gas fuelled, electric or District distribution. A sensitivity analysis is performed which revealed the influence of the price of electricity and PV panels. The classification system made the decision-making process easier for a possible investment in a solution. This classification system showed that the first three recommended solutions for investment are the houses H14, H17 and H20

Energy efficient houses began to be widely publicized after the oil crisis of the 1970s that led to an alarming increase in energy prices.This led to the development of concepts related to super-insulation, air tightness of the building, passive design and also the implementation of high efficiency heat recovery. The passive solar design for buildings was promoted by G. F. Keck with the “House of Tomorrow” (1933) and by MIT University with “Solar House 1” (1939) and later, the houses of the 1970s such as “Philips Experimental House” (Germany, 1975), “DTH Zero-Energy House” (Denmark, 1975), “Lo-Cal House” (USA, 1976), “The Saskatchewan Conservation House” (Canada, 1977), “Leger House” (USA, 1977) brought to the forefront issues such as super-insulation “super-glazing” air tightness, heat recovery ventilation. In the 1990s, in Germany a series of energy-efficient buildings were built, beginning with the building “Kranichstein” from Darmstadt as a result of the concept of “passive house” issued by W. Feist and Bo Adamson. Passivhaus Institut, founded in 1992 by W. Feist has three basic requirements for the certification of a passive house: Space Heat Demand (or, Heating Load) ≤ 15 kWh/m2/y (≤ 10 W/m2), Pressure Test n50 ≤0.6 h−1, and Primary Energy Demand (for all energy services)≤120 kWh/m2/y [1]. In addition to the basic requirements, some other rules of design are established, including: Average ventilation volume flow with ACH = 0.30 h−1 at least, indoor design temperature of 20°C, Heat recovery efficiency of at least 75%, use of the Ground-sourced Heat Exchanger, demand for Domestic Hot Water (DHW) to be partially or fully covered by solar collectors [1]. There is a point up to which intense thermal insulation ensures the maximum efficiency of the investment, which, if exceeded, leads to over-investment. In this situation one can calculate whether adding additional electrical panels to the passive house can be a more effective investment than over-insulation beyond the optimal point [2]. In 1992, Fraunhofer Institute of Solar Energy Systems (Germany) completed an “autosufficient house’, a building Off-Grid which produces the entire electricity it needs by means of PV panels [3]. In 1994 Rolph Disch built in Freiburg (Germany) the building “Heliotrope” with PV panels capable of producing 4-6 times more energy than necessary; this was among the first “Plus-Energy” buildings [4]. This new opportunity of increasing the energy efficiency as well as the economic efficiency of the investment by adding PV panels and by making the bidirectional connection to the electric network led to the need to develop the concepts of Plus Energy Building and Net-Zero Energy Building [5] and [6]. These types of buildings are taken in consideration in the study of this paper. In one year a Net-Zero Energy Building produces the same same amount of energy it consumes [7], while a Plus-Energy House produces more energy than it consumes, thus offering the opportunity to earn an income. Throughout the year for these buildings there is a monthly balance network monitored by a Net-Metering System and the factors taken into account are the weighting factors of import-export of electricity from the exchanges with the network [8] and [9]. The surplus energy exported to the grid is paid by the network operator [10], [11] and [12]. Starting from the targets imposed by international organizations and international treaties that promote environmental sustainability, the development of the residential sector is considering the use of renewable resources and the reduction of emissions of greenhouse gases. Thus, mention must be made of the Kyoto Protocol which obliged the signatory industrialized countries to reduce the emissions of greenhouse gases by 5.2% in 2010 as compared to the year of 1990 [13]; for the period 2013-2020 the protocol of Doha (2012) is agreed upon, to be fully adopted in 2015 [14]. In Europe, buildings consume 40% of the total primary energy and they emit 40% of all CO2 emissions [15]. This percentage is high and there are technical and legal resources to be significantly reduced. An EU directive issued in 2006 and approved in 2007 considered the following three goals: for the period 2006-2020 to reduce the primary energy consumption by 20%, renewables to reach a percentage of 20% and also for the period 1990-2020 CO2 to be reduced by 20% [16]. The widespread application of the Passive House concept will significantly contribute to the achievement of the objectives set at the European level. The European Climate Change Programme (ECCCP 2006) [17] identified the objectives and strategies for cost effective solutions, standards and energy efficiency measures for buildings. At the institutional level several incentives are given to investors in clean energy, including mechanisms that partially or totally cover the investment by non-reimbursable funds, green cards that over-pay the unit of clean energy produced, connection to public facilities, etc. Programs funded with support for energy efficient buildings catalyze the implementation of the European objectives [18]. The European Union Directive on the energy performance of buildings EPBD2010 [19] insists on increasing energy efficiency, by implementing passive heating and cooling systems and it uses the term “Nearly-Zero Energy” [20] and [21] for buildings that use renewable energy sources in a significant proportion. There are also requirements to achieve an optimum balance between investment cost and energy cost savings,a balance should lead to a reduction of the cost over the estimated economic life cycle, an aspect fully treated in the Supplementing Directive No 244/2012 [22], [23] and [24]. The use of alternative energy is indicated as a way of bringing the building's performance at an optimal cost level. Kurnitski et al. [25] and Hamdy et al. [26] exposed several calculation methodologies for buildings based on solutions of optimal cost. Among the requirements of a passive house, three aspects are of interest in this study and they are related to criteria of cost and energy efficiency: thermal insulation, renewable energy equipment and energy cost throughout the building's life cycle. The investment in a project such as a passive house does not mean only meeting a quality standard, but also meeting the criteria of sustainability (low energy and as well as energy from renewable resources, cost efficiency, concern for the impact on the community, environmentally friendly, beneficial ecological status, and even the use of recycled construction materials). The assessment of a house only by means of the quality-cost concept is not the most relevant because it is reduced only to the present time evaluation. The concept of cost throughout the life cycle of the building brings major contributions to the evaluation of a project by considering the present cost, the duration of use, the cost of operation, the interest rate, the escalation of the energy market price, the escalation of price for various systems and the inflation, in order to update the value of the building. Thus, it is necessary to underline the advantages of investing in an energy efficient house involving the cost over a period of the life cycle. The analysis of the life cycle cost (LCC) is particularly suitable for the assessment of building design alternatives that satisfy a required level of performance and can be applied to any capital investment decision where higher initial costs are balanced by future lower operating costs. The best technical efficiency leads to cost efficiency in operation when the criterion is energy, but in most cases a further acquisition cost is added and this makes the analysis based on life cycle methods necessary. In the studies carried out in the Polytechnic University of Bucharest a software CYCO-PH in VBA Code has been designed; based on the results of the balances from PHPP software (delivered by Passivhaus Institut), CYCO-PH is able to generate an analysis of the life-cycle cost, to make sensitivity analyses for the main results and to allow risk analyses for alternative projects. It is able to calculate the heat transfer through envelope based on the outdoor and indoor conditions such that makes possible sensitivity analysis. In portions of the alghoritms where are involved the equipments of the house, in its input are used directly the normalized values of the powers (thermal, electric) obtained from the output of PHPP where are applied the rigours of Passive House Institute from Darmstadt. Practically, it comes with an analysis that PHPP does not covers in the domain of economics and welcomes the European directives that aim to position the buildings in cost-optimal zones. Climatic data contain monthly normalized values of the temperature and solar radiation, particularly it was necessary to split the year in two seasons (cold and warm) and establish the average values for both in order to apply in the calculation the criterion that in winter to be assured 20°C and in summer 25°C (for at least 90% of the time). It is necessary to display information about the economic environment as the latter explains the information about the real conditions of the operation of an investment. A report by GTM Research for the period 2012-2017 provides a reduction of 38.8% of the prices of PV panels from 0.5 $/W (0.36 Euro/W) to 0.36 $/W (0.26 Euro/$) [27], a similar trend everywhere, which means an average reduction of about 17.2% (a negative rate of escalation) from one year to another for the respective period. If throughout the next 25 years prices varied with a constant escalation rate of 17.2% that would mean a price of 0.003 $/W at the end of the period; this value is too low and unsustainable. A more realistic forecast is to consider that in the next 25 years the price of PV panels will halve from 0.50 $/W to 0.25 $/W, which means a real average rate of escalation of the price of 0.027 (2.7%) from one year to another. Beyond specific prices $/W or Euro/W what is important are the trends in time that appear to be about the same for all countries. The escalation of electricity prices influences significantly the balance of the costs of an energy-efficient house and this is how the price escalation based on Eurostat statistics for the period 2007-2012 is considered (an average increase of 0.85% year on year [28]). In this paper are considered prices of fossil fuels (natural gas) of 0.28 Euro/kWh and also the price for heat from the District Distribution of 0.40 Euro/kWh. The forecast of the rate of energy escalation applies to all types of energy from industry (a simplification that includes solid fuel, gas fuel, electricity or mix of energy) and is 0.007 (0.7%) from one year to another for long term periods (more than 25 years). Eurostat [29] provides statistics about commercial interest rates (retail interest rate) which, for the period 2001-2011, was between 0.81% - 4.63% with a multi-annual average of 2.69%. However, in general, formal values of 3.0-4.0% are considered, and the most often used value (or required by official procedures) is 3.0%. Eurostat [30] shows an inflation of 2% in the last 20 years in Europe (in 2013 the inflation was of 1.6%) with a slightly descending trend and the value of 1.5% is considered the best estimate of the inflation for the next 30 years. In this study are very important the escalation of the energy price and of PV panels price, which are strongly related to issues of economic efficiency of the investment; these variables are kept as such for further use.

This paper reproduces the economic model of the Passive House POLITEHNICA of Bucharest at the parametric level; the latter allowed subsequent technical variations by adding and removing equipments that affect the final energy consumption. The software CYCO-PH was built at University POLITEHNICA during this study. This software is specialized in analyzing heterogeneous solutions of investment projects in buildings that include renewable energy systems, particularly PV panels for the production of electricity, solar collectors, heat pumps, etc. A comparative analysis of a range of solutions of houses, among which are a standard house (H12) and the Passive House POLITEHNICA (H19), was made by means of several criteria of cost that are significantly influenced by energy efficiency. All these criteria were finally abstracted in a classification system that helps investors to choose the best solution for their purpose. We concluded that the recovery of the additional investment in alternative and energy-efficient solutions in comparison with a standard house can be achieved in 16-33 years by a conservative assessment or in 16-26 years when the best forecasts of the economic conditions are considered. The base case itself influence accordingly the results of evaluation: if standard house have the solution of heating and DHW based on gas fuel then payback time is achieved in 16- 26 years; if heating and DHW is based on electricity then payback time is achieved in 9-16 years; if heating and DHW is based on District Distribution then payback time is achieved in 16-28 years. As noted, the District Distribution system remains the most difficult to be replaced by renewable energy systems applied to the buildings. The sensitivity analysis with the deterministic approach has imposed scenarios of variation from the uncertainty of the economic environment, sketching possible ranges for the monitored parameters (LCC, DPBT). This analysis can be completed in the future through an approach that includes risk analysis. The price variations from country to country and also from year to year are wide (for renewable energy systems in general and for PV panels in particular) and this can be a special research topic. Beyond the interpretation of the results of this research paper, every investor may prepare its own decision based on its goals. The life-cycle cost method used in this study was able to provide useful information and a new approach to potential investors (individuals, institutions, companies) that can be used in their projects.