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Final Report Summary - DEMAG (Domestic emergency advanced generator)

The DEMAG project intended to investigate the indoor domestic application of advanced hydrogen technologies to life saving emergency energy generators, and deliver an emergency power supply, rated 10 kWh, based on the integration of a PEM fuel cell with ultracapacitors and with a metal hydrates container for hydrogen storage: the FC is expected to provide a basic power output, whereas ultracapacitors can supply temporary peak loads.

The future reliability of centralised energy supply is questioned by energy experts, authorities and final users. In current large scale interconnected supply grids a problem in any portion of the massive generation, transmission and distribution chain can leave customers in a wide geographic area without power and vulnerable.

Weaknesses can affect electricity distribution from several origins (costs of fossil fuels, need to reduce greenhouse emissions, reduced water availability due to global warming, lack of maintenance of electricity grids, etc.), all factors which are supposed to have an increasing impact in the future.

An Emergency power supply (EPS) with a rated capacity of at least 10 kWh based upon existing accumulator technologies is clearly unfeasible and impracticable for weight and size reasons; keeping such an amount of chemical batteries in a house would be a non-sense.

The tangible outcomes that the DEMAG project aimed at were:
- 10 kWh emergency power supply, able to supply 1 kW during 10 hours;
- 220 Volt at 50 Hz power output;
- power generation by means of a 1 kW PEM fuel cell;
- weight < 100 kg (including hydrogen storage, energy generation by PEMFC, controllers, auxiliaries and ancillaries);
- volume < 12 litres (including hydrogen storage, energy generation by PEMFC, controllers, auxiliaries and ancillaries);
- safe energy storage through a state-of-the-art metal hydrates LaNi5 hydrogen tank, operating at 2 bar and room temperature;
- automatic start-up during black-out and shut-down on grid reconnection;
- flexible and easy installation both for new installations and retrofit;
- able to supply a load exceeding the rated power for a limited time, thanks to the integration with ultracapacitors, (e.g. start-up of the compressor of a refrigerator, the inductive starter of a fluorescent lamp, or the charge of a capacitor in a switch power supply), while the system alerts the users by means of a warning sound; if the extra load persists, DEMAG will interrupt the supply for some seconds, allowing the users to remove the extra loads;
- usable also as a portable power generator, powered by a small size lighter hydrogen tank.

The work performed in the project was split in the following Work packages (WP):

WP1 EPS operative specifications
a) A test bed for direct measurement of domestic load profiles has been designed and prototyped. This experimental data acquisition layout has been used to measure load profile absorption, both in transient and steady regime, of several critical and non-critical domestic devices.
b) Domestic loads have been categorised in four priority classes. This information are used by the controller to implement the load management strategy and to disconnect selectively different loads.

WP2 Design of hydrogen storage tank
a) The adsorption / desorption reaction of hydrogen in metal hydrides has been studied so as to define the storage module dimensions (weight and volume) needed for DEMAG project and the mass and energy fluxes needed for its operation.
b) A market survey, to identify off the shelf metal hydride tanks, has been performed and a suitable device for hydrogen storage has been selected.

WP3 Design of the central unit
a) A central unit, able to produce up to 10 kWh of electrical energy has been designed on the basis of a PEM fuel cell, and a metal hydride commercial storage tank.
b) An intelligent DC-DC converter, able to coordinate the power contributions coming from the fuel cell and the supercapacitors pack has been designed.
c) An electronic controller, integrating the communication with peripheral units, and allowing the correct implementation of start-up and shut-down of the DEMAG system and the load management strategy, has been designed.

WP4 Design of peripheral units
a) An intelligent master switch interface has been designed in order to disconnect the domestic environment from the power grid in case of blackout, and to reconnect safely when the main power is back.
b) An automatic disconnection module, with the twofold objective of providing remote disconnection ability to the central unit and monitoring power demand has been designed.

WP5 EPS prototyping
The DEMAG EPS has been prototyped, and it is installed for testing in Labor's laboratories.

WP6 Testing
a) DEMAG EPS has been thoroughly tested, and several improvements have been identified and / or implemented to optimise its efficiency and improve its behaviour.
b) Results have been widely assessed among the partners. The technological feasibility of the DEMAG concept is accepted, while there are still concerns for what regards the economic.

WP7 Safety assessment
A thorough report, addressing the normative framework in the fuel cell and hydrogen related technologies has been issued, with focus on the components used in DEMAG.

WP8 Dissemination and exploitation
a) Exploitation and marketing strategy were defined, along with the routes for future research and development activitie. sb) The dissemination measures carried out in the second year of the project include:
- fairs, workshops and meetings;
- a webpage for the dissemination of the aims and results to the wide public;
- contacts with potential customers.

A complete communication system, based on Zigbee technology, have been designed as a framework to enable an intelligent management of the DEMAG system.

The central unit (CU) is therefore able to communicate with peripheral units to detect device failure, mains blackout, load power absorption for each device; moreover the CU is able to interact actively with peripheral units to implement an intelligent selection of the loads to be supplied, based on their priority, and to provide secure reconnection when the main grid is back.

The DEMAG modular architecture, consisting of a central supervising unit and peripheral devices incorporating different functionalities, could be exploited in traditional backup systems, with the following advantages:
- It allows designing the size of the backup power for emergency loads and not for the nominal power of the domestic grid, since it provides the capability to disconnect unnecessary loads.
- It allows placing the central unit detached from the main switch.
- Is ideal both for new installation and for retrofit of existing grids.

The wireless communicating devices have a lot of functionalities, which could be interesting in the design of backup systems. In principle, a module providing such auto-diagnostics and communication capability with a master supervising unit can be used, for example in hospital or emergency centres, to exclude non-critical loads from the power grid, when the emergency backup power is used.

The DEMAG devices have been designed to read the current drawn from the power grid, but they could be modified with the aim of hosting several kind of sensors like temperature, humidity, acceleration, or anti-intrusion, and they could be much effective in implementing a central monitoring system over remote environment.

The consortium of the DEMAG project has designed and developed a hybrid power generator based on the integration of PEM fuel cells, supplied with hydrogen from metal hydrides tanks, and electric power buffer ancillaries (like batteries and super-capacitors).

The DEMAG generator is used to supply power to the domestic grid, in case of blackout, through any outlet of the electrical system, and the main characteristic of the power train deployed in this application is to avoid the fuel cell to be forced to sustain highly dynamic load, and peaks over the nominal power of the FC, since the variable power supply is one of the main reasons of the stack lifetime reduction.

Indeed the architecture of the DEMAG generator is able to convert power spikes, typical of load insertion into domestic grid outlet, in quasi-stationary variations of FC power demand, using super- capacitors as ancillary power storage system. An intelligent DC/DC converter manages intervention priority of power components.

Moreover, a supervisor is able to interact with the peripheral units providing the DEMAG system with the intelligence needed to manage the interaction between loads and the generator. A prototype of the overall DEMAG system has been built and is available for demonstration runs.

The main market application of the knowledge generated under the DEMAG project is the design and production of FC-based domestic solutions for replacing traditional battery in non-critical backup power applications, i.e. when the continuity of power supply is not required.

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