In July 2018, a two-year monitoring of the FENIX Group a.s. in Jeseník. During this time, different operating modes of the battery were used to test their capabilities to ensure the power operation of the object. This article describes the entire period in terms of energy flows in the building. The main parameters are energy consumption, supply to the grid, self-sufficiency of the building from the photovoltaic source and local use.
A number of articles have already been written about the building, with details about the construction and energy aspects [1, 2]. Therefore, the description of the energy management in the building will only be given to the extent necessary for a general view of the energy of the building.
1 Brief description of the energy concept of the building
The office building of Fenix Group a.s. in Jeseník was designed and built in the standard of a building with almost no consumption. The only energy carrier is electricity, which is extracted from an adjacent production area that is connected to the distribution network spool (DS). CEZ. Electricity serves to ensure the functioning of the building – ventilation, cooling, heating, TV preparation, use of typical equipment that is typical of an office building (office equipment, IT …). Because it is an office space with designated traffic, it is very good to predict how the building is being leaked, in contrast to residential homes. A large part of the electricity is also obtained locally from a photovoltaic (PV) source. It covers all the available roof surface, the output is 7.28 kWP. As stated in the following chapters, the energy produced in this way is used locally locally for the operation of the building. This is due to the character of the administrative building (in the case of residential homes a considerably lower local usage ratio is reached by 25-60%) and by the use of a battery storage (Li-ion technology, usable capacity of 20 kWh).
Battery storage supplies energy directly in the internal distribution of the building. The battery charge is regulated separately for each of the three phases of the internal distribution. Charging / discharging of battery management is provided by a customized MaR system. It uses forward energy calculations, using the prediction of the production of the PV plant and the prediction of consumption in the building, taking into account the selected regime, energy tariffs and preferences of the operator.
The functions of the hybrid photovoltaic system (HFV) are as follows:
- Increase in local use of PV energy (index Fat)
- Move the flow from DS to low tariff times
- Limit of sampling peaks (DS power limit)
- Provide Traffic at Power Dissipation (UPS)
- Controlled power supply to DS (DS support)
The following conditions may occur during operation:
- Full coverage of subscriptions to buildings from your own (FV) source,
- 1.1 excess energy is supplied to the battery
- 1.2 surplus energy is delivered to the distribution network
- 1.3 the production of PV sources is limited
- Partial coverage of the starts of buildings from the own (FV) source,
- 1.2 the remaining energy required is covered by the battery
- 2.2 the remaining energy required is covered by the distribution network
- 2.3 the functioning of the building is limited
Commonly used modes are marked, mode 1.3 was only used from the beginning of the monitoring period and then it was decided to supply surplus power to the network. Mode 2.3 is used to a limited extent – TV preparation (TV magazine with electric heating, building is a small TV) and heating of the selected part of the parking lot (crucial part of the access area for the power supply).
2 Determination of the operating parameters
A simplified scheme of energy flows is evident from FIG. 1. The electricity meter at the inlet of the building measures the total consumption (ODB) and energy supply outside the building to an associated industrial site (Dod). Total consumption of buildings (sp) is measured by a system of secondary energy meters and the energy supplied by the PV system (FV), battery power (BatDod) and energy from batteries (BatOdb).
FIG. 1: Simplified scheme of energy flows in the building
We will determine our own self-sufficiency in the monitored period based on the measured energies, Fig. 1. However, it is necessary to determine how HFC system losses and energy outflows in a building must be processed (Dod). The first option is to take into account the theoretical self-sufficiency whereby the losses of the HFC system are not taken into account and the overflows within the net sensor are deducted from the consumption. Then we express the self-sufficiency of the building as
In the real case, losses on the HFC system must also be taken into account, taking into account the fact that the energy supplied to DS is not used in the building. We get self-sufficiency like
However, losses in the HFV system can be taken into account in the event that the building's consumption is used (technical consumption of the energy system), since the full HFC system fulfills a number of the above functions, not only the local use of PV energy. This is how we express our self-esteem as:
Another parameter is the local index for energy consumption that is produced on the basis of the PV source, which indicates the share of energy consumption in the building on the total energy produced by the PV system:
3 Biennial monitoring results
First let's look at the structure of energy consumption in the building, Fig. 2. The dominant component of the collection is heating, which is seasonal (November – April / May). Other subscriptions are almost constant throughout the year, including sockets, auxiliary circuits (mainly the data rack). Subscription to the rest of the circuits is no longer significant.
FIG. Figure 2: Structure of consumer areas in an office building
FIG. 3: Object consumption and production of PV sources
Assuming that all energy produced by the PV system (FV) will be used in the building and the HFC system will have no further losses, we will extract from the data in FIG. 1 theoretical self-reliance during a two-year operation
FsTor = 13.3 / 49.7 = 26.8%. The energy consumption in the building and its production in individual months is shown in Fig. third
FIG. Figure 4: Indices of self-sufficiency and self-sufficiency of PV energy
autarky Fs1 is significantly lower (14.9%). We can use a good compromise when assigning HFV system losses to consumer buildings Fs2 (24.7%). Indices for individual months are shown in FIG. 4th
It should be noted that electricity is the only form of energy for the building (use for heating / cooling and TV preparation) and the building has an administrative character (high requirements for ventilation and operation of office equipment on working days, low TV consumption). Moreover, thanks to the three floors, the roof area for the PV system is limited in relation to energy consumption. Major heating needs during the winter season are due to controlled electrical heating (radiant ceiling panels, wall panels, underfloor heating), ventilation requirements to ensure an incoming climate of high quality and a local climate (Jesenik). Therefore, self-supply values can not be expected, as in the case of low-energy or passionfamily houses with a single floor occupied by only a few people.
FIG. 5: Indices of self-sufficiency and own use of PV energy in the selected month in April 2018 (weekends are marked)
The local PV power index is Fat = (13.3 – 1.0) / 13.3 = 92.2%, which is a very good value. Most of the energy is used in the building, with the exception of small overflows to DS in the late spring and summer. FIG. 5 confirms the assumption that, due to the nature of the office building, energy surpluses occur in DS, especially during the weekend. In this example, the value is Friday on sunny days Fat lower due to limited operation (large surplus energy) and Monday due to pre-charged batteries of the weekend.
FIG. 6: Structure of the total energy that is used in the building after months
FIG. 6 shows the composition of the total energy in the building in each month. During the summer period, most of the energy is obtained from the PV source, while in the winter months the DS is dominated to a large extent by the SS. In some winter months (November 2017 – February 2018) the losses of the HFV system in delivering the balance functions of an object outweigh the production of PV power (delivery of the HFV system is negative).
FIG. 7 shows the energy balance of the entire monitored period. There are significant losses in the HFC system, which were 4.9 MWh during the two-year operation. It is divided into losses in batteries (0.6 MWh) and losses in hybrid converters (4.3 MWh).
FIG. 7: Composition of the total energy used in the building during the monitored period (kWh)
The batteries were heavily used during the monitored operation – they protected 10.9 MWh of electricity, the efficiency of the cycle (charge + discharge) was 95%. With regard to the battery capacity, there were 545 complete cycles, i.e. an average of 0.7 cycles per day.
Losses in hybrid converters can be divided into energy losses due to power consumption by inverters and loss of efficiency at load. The estimation of the energy loss due to the power consumption of the inverters can be made on the basis of the number of operating hours, the number of inverters and the typical values specified by the manufacturer. We get the energy value E = 17 520 h × 3 × 22 W = 1.2 MWh. The remaining part (about 3.1 MWh) is a loss of energy due to the load on the inverters (loss of DC / AC converter, filters …).
The energy system in the Jeseník office building is atypical with its extensive range of modes and functions to ensure both operator energy savings and DS support. The batteries are strongly affected by this operation. Because they are designed for 5,000 complete cycles, they are not expected to change in the coming years.
For the HFV system operator, the above scheme only makes sense if the DS service provider finances or otherwise funds the support services in an appropriate manner. This is a matter of the concepts of smart grids, active building energy and their operators in the role of the so-called prosumer (current producers and consumers). Everything is, of course, linked to legislation and the ongoing liberalization of the energy market. Even the building in this respect took a small step forward. In collaboration with the ČEZ distribution, a joint test was conducted in June 2018 to verify the concept of supported services for remote support and the impact on network quality. Measurements have been successful, detailed results will serve stakeholders in further development in smart energy areas and will be presented at expert conferences or workshops.
Frequent energy balance in the building and DS support is reflected in increased energy losses in the HFC system, as shown by the measured data. Losses occur mainly on the side of the converter, with a large share in the case of their own operation in the on-state. Used batteries showed good cyclic efficiency (95% measured).
The monitoring of the object will continue after this basic and key period. Business modes will be further aligned to take into account current developments in smart energy and trends in the use and integration of renewable energy sources in buildings, with a strong emphasis on monitoring the current battery life and the lifetime of the battery. battery.
This work was supported by the NPU I program no. LO1605 – University center for energy efficient buildings – Sustainability phase.
- Urban, M .; Bejček, M.; Wolf, P .; Vodička, A. Concept of an administrative building as a building with almost no energy consumption. Heating, ventilation, installation. 2017, 26 (1), 30-36. ISSN 1210-1389.
- Wolf, P .; Novák, E.; Včelák, J.; Urban, M. The administrative building of the Fenix Group TZB HAUSTECHNIK SK. 2017, XXV. (3/2017), 24-27. ISSN 1210-356X.
Two years of use of the Fenix office building in Jeseník – view of the energy balance
In July 2018, a two-year monitoring of the FENIX Group a.s. in Jeseník. During this time, different operating modes of the battery were used to test their capabilities to ensure the power operation of the object. This article describes the entire period in terms of energy flows in the building. The main parameters are energy consumption, supply to the grid, self-sufficiency of the building from the photovoltaic source and local use. A number of articles have been written about the building, with details about the construction and energy aspects [1, 2]. Therefore, the description of the energy management in the building will only be given to the extent necessary for a general view of the energy of the building.
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