444
A. Halász et al.
31.2.1 Storage Possibilities in Nanogrids
It is worth to note that not only batteries can be used as energy storage systems for the
nanogrids but other types of energy storage systems. Beside the well known battery
types of lead-acid and lithium batteries one of the newest is the so called redox-flow
battery. Also supercapacitors (or also called ultracapacitors) can be used, which also
has several types like electrostatic double-layer capacitors (EDLCs), electrochemical
pseudocapacitors and hybrid capacitors. The mechanical possibilities are flywheels,
pumped-storages (hydroelectricity) and compressed air energy storages (Blaabjerg
and Ionel 2017; Vilathgamuwa et al. 2011; Du et al. 2007; Zhang et al. 2012). The
fact that one office as nanogrid has a relatively small energy storage demand makes
it possible to use different storage types.
As our measurements shows for an office with two laptops with two external
monitors and two phones a battery with a capacity of about 680 Wh and two 1.5 m
2
polycrystalline PV cell could be sufficient (Cserép et al. 2017). According to the
measurements and calculations such a configuration can run the ICT devices trough
the day even in winter when there is no direct sunlight on the PV panels.
31.2.2 Including ICT Device Batteries as Storage
Some of the ICT devices as laptops and mobile phones has a built in battery for
their operation. The extension to the previous concept is to involve these batteries in
the operation of the nanogrid. The mobility of these devices makes it necessary to
have information if the user will use the devices out of office. The possible highest
charge level should be provided for extended out of office usage. To provide this
functionality the energy storage management system (ESMS) of the nanogrid should
get information from the users calendar events to estimate the necessary time for
charging the devices battery for the highest possible level. If the devices are used
in the office the ESMS of the nanogrid can provide charging if sufficient energy is
generated by the PV cells or switch off the power for the devices and force operation
on the built in battery in case of low energy generation by the PV cells.
To the already presented constraints a further constraint is introduced which are the
timetables of the users of ICT devices. These makes the control even more complex.
31.2.3 Battery Charging Estimations
To be able to estimate the charging process some information are necessary about
the batteries from the devices and the energy storage of the nanogrid. The type of the
energy storage, the capacity of the storage and the state of charge (SOC). The type
and age of the energy storage lays down the state of health (SOH) and the state of life
A. Halász et al.
31.2.1 Storage Possibilities in Nanogrids
It is worth to note that not only batteries can be used as energy storage systems for the
nanogrids but other types of energy storage systems. Beside the well known battery
types of lead-acid and lithium batteries one of the newest is the so called redox-flow
battery. Also supercapacitors (or also called ultracapacitors) can be used, which also
has several types like electrostatic double-layer capacitors (EDLCs), electrochemical
pseudocapacitors and hybrid capacitors. The mechanical possibilities are flywheels,
pumped-storages (hydroelectricity) and compressed air energy storages (Blaabjerg
and Ionel 2017; Vilathgamuwa et al. 2011; Du et al. 2007; Zhang et al. 2012). The
fact that one office as nanogrid has a relatively small energy storage demand makes
it possible to use different storage types.
As our measurements shows for an office with two laptops with two external
monitors and two phones a battery with a capacity of about 680 Wh and two 1.5 m
2
polycrystalline PV cell could be sufficient (Cserép et al. 2017). According to the
measurements and calculations such a configuration can run the ICT devices trough
the day even in winter when there is no direct sunlight on the PV panels.
31.2.2 Including ICT Device Batteries as Storage
Some of the ICT devices as laptops and mobile phones has a built in battery for
their operation. The extension to the previous concept is to involve these batteries in
the operation of the nanogrid. The mobility of these devices makes it necessary to
have information if the user will use the devices out of office. The possible highest
charge level should be provided for extended out of office usage. To provide this
functionality the energy storage management system (ESMS) of the nanogrid should
get information from the users calendar events to estimate the necessary time for
charging the devices battery for the highest possible level. If the devices are used
in the office the ESMS of the nanogrid can provide charging if sufficient energy is
generated by the PV cells or switch off the power for the devices and force operation
on the built in battery in case of low energy generation by the PV cells.
To the already presented constraints a further constraint is introduced which are the
timetables of the users of ICT devices. These makes the control even more complex.
31.2.3 Battery Charging Estimations
To be able to estimate the charging process some information are necessary about
the batteries from the devices and the energy storage of the nanogrid. The type of the
energy storage, the capacity of the storage and the state of charge (SOC). The type
and age of the energy storage lays down the state of health (SOH) and the state of life