Studio ing. Maurizio Forcieri – OIMB n° A1913 – piazza Gramsci 4 – 20835 Muggiò (MB)
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Patent Application – Draft issue #1 April 19th, 2012
Household Appliance for Fast, Smooth Charge of Electric Car
1 Bibliographic Information
Acronym:
“HAFSCEC” = Household Appliance for Fast, Smooth Charge of Electric Car
Keywords:
household appliance, household mains, all-electric car, battery charge, ...
Author & Applicant:
dr. ing. Maurizio Forcieri – piazza Gramsci 4 – 20835 Muggiò (MB – Italy) (free-lance)
phone: ++39.39.2789287 mobile ++39.335.6919645 or ++39.338-6517117
e-mail: maurizio.forcieri@alice.it, certified e-mail: maurizio.forcieri@ingpec.eu
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2 Abstract
The patent application addresses a household appliance for fast, yet smooth charge of batteries of
100% electric cars, namely: (i) on the mains side it complies with the technical and contractual
constraints of a typical “household”, with power limited to a few kW, (ii) and on the car side it fully
exploits the car battery’s capacity and charging profile.
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3 Description
3.1 Technical Field
The invention fills a gap, which at present contributes to hampering the onset of fully electric cars:
that is, the incompatibility between the high power required to charge the batteries in a reasonable
time, and the low power (in Italy: 3kW) offered by utilities to “household” type of users.
The solution is simple: store power (≤3kW) drawn from the mains, 24 hours a day, 7 days per week,
into a stationary battery of adequate size (amply exceeding that of the car); and while the car is
plugged-in for recharge, draw power both from the stationary battery and (as available) from mains.
3.2 Background Art
Surprisingly enough, in an apparently blooming market, to date no such device has been offered.
The only product somewhat similar, announced by Giulio Barbieri S.p.A. (www.giuliobarbieri.it) is
“Self-Energy”: a carport with: (i) photovoltaic panels (ii) stationary batteries with their (iii) charger
(iv) a DC/AC inverter (v) car battery charger. From the website data, however, we can remark that
power is mainly drawn from the PV-array, and only exceptionally (i.e. to avoid too deep discharge)
from the grid: the grid seems required more as a 220V 50Hz reference common to both (iv) and (v),
than as a “mains” power. Items (iii), (iv) and (v) look like just individual, commercial-off-the-shelf
(COTS) pieces of equipment joined together and, apart from optimising PV-power e.g. with MPPT,
it seems unlikely for mains power to be optimised too, e.g. to cater for prevailing power demand by
other household appliances (e.g. laundering, cooking,...): indeed, this is not a household appliance.
A quich search reported a couple of patents by Giulio Barbieri S.p.A., however limited to the field
of metal structures, joints etc. – nothing to do with power.
On the other hand, a patent application in this field was published as recently as March 8th, 2012,
with priority September 6th, 2010, under n° US2012056588(A1) and title: “Use of Battery Energy
for Power grid Optimisation and Electric Vehicle Charging”. A careful review of its description and
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claims shows however some major differences (we report the original text with our own highlights):
• § [0010] that summarises the background, stresses that “there has not been any system
available than can provide both DC fast charge and grid optimisation”: this is consistent
with their challenging goals in terms of performance and reliability (see below), whereas we
focus on a small appliance whose primary purpose is just to charge the car – to return power
to the grid is just an opportunity;
• § [0012] specifically addresses a “high voltage” grid connection, whereas ours is a typical
“low voltage” (monophase) for household; now, disregarding some well-known differences
between the US and the EU grid systems, the meaning of these two sentences is quite clear
on either side of the Atlantic and unambiguous to anybody skilled: they identify mutually
exclusive categories, in both technical and contractual/regulatory terms;
• § [0026] describes a redundant “array of battery cells arranged in parallel-series-parallelseries format that provide the highest reliability, robustness and serviceability”: apart from
concerns about the feasibility of such parallel connections, not wholly cleared by the notion
of inductive instead of resistive balancing in § [0035] (all the more if brand new cells may
be added in parallel with existing ones at a later stage – see § [0029]) such an arrangement,
jointly with sophisticated cell-level monitors and management, is consistent with the very
ambitious performance, but largely exceeds the requirements of a household appliance;
• § [0034] further stresses the huge size of such system (“a fully charged battery matrix can
discharge 6 MW of power for 20 minutes, enough to provide electricity to 6000 homes for
half hour”): such performance is consistent with, and confirms, if ever need were, the above
sentence i.e. the grid is – and must be – “high voltage”, as the power exceeds by three orders
of magnitude the throughput of household mains: this system is not only oversized and most
likely un-economical, but absolutely incompatible with low-voltage household mains;
• the Claims do not (re)define the scope of invention with their own self-standing words, but
simply refer, by saying “as shown and described”, to the technical body (text and drawings)
with its unique scope; also, the sentences in § [0041] & [0042] do allow for some flexibility,
but obviously do not, and could not, broaden the scope to a qualitatively different one: hence
the Claims inherit and itemise as scope of the patent the unique features highlighted above;
• in conclusion, we do believe that the scope of US20120056588(A1) is limited to that just
described, namely: on the one hand, to “high voltage” grid connections (i.e. multi-megawatt
peak power, redundant battery array etc.); and (that means: logical intersection of sets) on
the other hand, to applications that feature “both DC fast charge and grid optimisation” .
Summarising the above, US2012056588A1 is also definitely not a household appliance.
(We are not aware of the relative timing between the announcement of Giulio Barbieri’s product and
the patent application mentioned above).
In conclusion, we trust that we can still claim as distinguishing features of HAFSCEC:
⎈ purpose essentially to recharge the car battery – optimising the grid power is an optional;
⎈ reliance on power available from the utility mains (whatever its primary sources: fossile,
fissile, or renewables) – whereas power from household PV or windmill is an optional;
⎈ compliance with household constraints (and possibly smart use of dual day/night tariff).
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3.3 The Invention
3.3.1 Technical Problem
As a foreword, we disregard “hybrid” cars equipped featuring both an electric and a thermal engine:
fashionable and much advertised but, to the author, not at all “green” or, worse, even harmful for the
environment, owing to their huge size, power and mass, further aggravated by electrical hardware.
We shall rather focus on all-electric cars: small, light, designed for “commuter” kind of trips, e.g.
from home to work on a daily basis, however required to be ready at any time for un-planned needs.
We assume a round-trip of 80 km per day in a mixed urban-suburban traffic, in daytime. For a small
car, this means some 10 liters = 8 kg gasoline per day (8 km per liter). One kg gasoline yields about
5 HP-hours net to the shaft: consequently we need 40 HP-hours = 30 kWh per day, net at the shaft.
We assume that, while riding, the overall powertrain (onboard battery→electronics→engine→shaft)
efficiency amounts to 80%: therefore we need to store 37,5 kWh electrical into the onboard battery.
This rather low efficiency figure is mainly determined by ohmic losses in copper, in the electrodes,
and within the electrolyte itself, which heavily depend on the current profile; and also by hysteresis
losses in engine iron. Losses in the drive electronics may account for at least 5% average. We do not
take into account kinetic energy recovery upon braking as this is marginal and depends on driving
habit and on the traffic – at low speeds there is little to recover.
We also assume that the (mains→AC/DC converter→onboard battery) charging efficiency amounts
to 95% (a relatively high figure, thanks to smooth charging profile, limited anyway by the 3kW)
assuming a straight plug-in cable, rather than an inductive coupling that would be much lossier.
Consequently, to fully charge the onboard battery takes longer than 13 hours: hardly acceptable if
one is in a hurry, or just wishes to use the same car also in the evening; and anyway still is subject
to conflicts with household demands and mains availability.
3.3.2 Solution
The solution is straightforward: use a stationary battery (item 2. in the drawings) as a buffer.
We assume that, while car is parked, the (stationary battery→DC/DC converter→onboard battery)
charging efficiency amounts to 80% – this figure is conservative, owing to the higher ohmic losses
for a high charging rate: therefore we have to draw 46,88 kWh electrical from the stationary battery.
We finally assume that the (mains→AC/DC converter→stationary battery) charging efficiency
amounts to 95% (this figure is higher, thanks to smoother charging profile over 24 hours per day).
Therefore we have to draw from the mains something close to 50 kWh per day. Under the 3kW
constraint, this would take 16 and a half hour, i.e. 70% over the 24 hours, which sounds compatible
with the integrated daily household demand. Drawing on the stationary battery, the time to charge
the onboard battery is only limited by the latter’s technology – typically a couple of hours.
So far, capacity margins. i.e. power reserve for additional mileage, self-discharge over long stays,
and max. depth of discharge, are not accounted for. In particular, dealing with the stationary battery,
the margin w.r.t. 100% depth of discharge depends on technology – in case of a most conventional
lead-acid battery it would be in the order of 25% to avoid irreversible damage, therefore the actually
required capacity should be another 25% on top of the 46,88 kWh giving nearly 60 kWh. However,
this extra capacity does not affect the daily budget of power drawn from the grid.
The figures are summarized in the following table (NB: all the figures as such are given just for the
sake of showing the problem and the solution, but shall not be binding for the patent purposes, and
could be downsized or oversized without harm, save however the constraints of a household and
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charging a single car at a time).
daily round trip (km per day)
(equivalent) gasoline yield (km per liter)
daily gasoline consumption (liters per day)
gasoline density
daily gasoline consumption (kg per day)
gasoline energy yield (net shaft HP-hour per kg)
energy consumption (net shaft HP-hour per day)
equivalence kW per HP
energy budget (net shaft kWh per day)
overall powertrain efficiency (onboard battery→electronics→engine→shaft)
energy budget for onboard battery (kWh per day)
charging efficiency (stationary battery→DC/DC converter→onboard battery)
energy budget for stationary battery (kWh per day)
(mains→AC/DC converter→battery) charging efficiency
mains energy budget (kWh per day)
household mains power (kW)
time to fully charge stationary battery (hours)
fraction of time
time to fully charge onboard battery directly (hours)
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0,95
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Smart power management
Obviously, the nearly 70% duty rate w.r.t. the daily energy budget of household mains cannot be
exploited bluntly: it takes a smart power management to give priority to the most urgent users.
Priority is normally for household appliances: in which case, if they require in total less than 3kW
(one cannot anyway turn on an oven and a washing machine at the same time, as each takes 2 kW)
HAFSCEC could still keep charging at a lower rate – which is anyway beneficial for some batteries.
(In case of urgency however one may wish to draw a flat 3kW entirely for the car, without climbing
from the garage upstairs to switch off each and every appliance at home: in which case he may do
so directly from the HAFSCEC control panel).
A few modern houses might be equipped with state-of-the-art smart power management devices,
but we cannot rely on this assumption: therefore we assume just a simple electrical system, with the
required protection devices against short-circuit and electrocution (e.g. in Italy by Norme CEI) but
otherwise not “smart”, nor split into individually switchable and protected sub-sections. Therefore,
smart functionalities required to optimise the use of power and comply with household needs shall
be implemented as an integral features of HAFSCEC itself. This implies an integrated complex of
electronics (item 1. in the drawings) that include a current meter (item 1.1.) to measure the power
instantaneously required by other household appliances; a smart controller (item 1.2.); and an MMI
(man-machine interface, item 1.4.) together with the required switches (=manual switches + relays).
Individual household vs. condominium
We assume that the low-voltage grid connection comes conveniently through the house basement,
where counters are most often located (even in condominia): this means that connecting HAFSCEC
for each individual tenant, through his own household counter, is relatively easy.
On the contrary, the notion of a “big HAFSCEC” shared among the tenants of a condominium does
not look that attractive: it would not grant major savings in mass, size and capital, unless the users
are time-shifted, because the capacity of the stationary battery should still cater for the sum of all
individual needs; and it would not easily overcome the 3kW constraint, unless the condominium has
a larger supply contract on its own (but usually this is set aside for lights and elevators, which shall
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not be compromised, for safety reasons). Passive safety requirements of HAFSCEC itself (fire etc.)
would apply in full, owing to the large power and stored energy stored. Overall, we think that such
an investment, and its operations and maintenance recurring cost, would hardly be manageable
under the consensus rules of a condominium and would soon raise controversial issues.
Option – Integration with Renewable energy sources
Availability of renewable energy sources, e.g. photovoltaic panels and wind mills, as part of the
house itself, is an opportunity considered here without harm to the basic idea, namely: charging the
all-electric car’s battery primarily relies on the power supply from the mains, which is contractually
limited, but guaranteed available 24/7.
The opportunity arises, at least in Italy, from the recently announced trend (i) by the Government, to
reduce subsidies in favour of electric energy produced from renewable sources, (ii) by the energy
Authority to further penalise it owing to its unpredictability (an argument that sounds questionable,
because, since a decade, the peak demand occurs in working hours of sunny summertime days when
air conditioners run flat, but also PV power is at a reasonably predictable peak; and is contradictory,
or at least redundant, w.r.t. the dual tariff that also penalises daytime use).
Under this trend, the only way for producers of electrical energy from renewable sources to avoid
the penalty is to become themselves predictable and use large storage (typically batteries) as buffer.
A further element of this trend is a requirement for power factor optimisation by small producers,
i.e. that any required reactive power shall be compensated locally. This means that the HAFSCEC
own inverter shall not only measure the current drawn by other household appliances, but also its
phase, and compensate for the quadrature component.
These new requirements would imply heavy and expensive retrofit to a wealth of existing inverters.
Incidentally, 50 kWh is roughly the peak energy available daily from a household PV array in June:
at latitudes around 45° an optimally exposed array gets nearly 6 kWh/m 2/day incident radiation
(data from http://www.solaritaly.enea.it/) that with an overall conversion efficiency (PV+inverter)
around 20% delivers 1.2 kWhel/m2/day; hence 50 kWhel/day means a rather large PV-array of 40 m2.
If this is the case, the battery already available in HAFSCEC, compatibly with its primary use, that
is to store energy from the mains in order to later charge the all-electric car’s onboard battery, can
also be used as a buffer between PV or windmill and the utility. This requires:
• an optimised topology of the converter electronics: since most existing PV- or windmill-own
inverters do not cater for storage, a solution is that the HAFSCEC’s own AC/DC converter
that normally charges the battery from the mains would also work the other way round;
• a new functionality in the smart controller, that allows the user either to set aside 100% of
the stored energy for its primary use, or, to allow to use it partly (up to TBD%) for a timely
and well-balanced return of energy to the mains: this requires a forecast of the energy offer
from renewable suurces, and of demand from the grid, that’s why we also foresee an internet
connection (item 1.5. in the drawing B) assuming that the Authority will provide for such
data to be broadcast in a machine-readable format.
In this case, HAFSCEC also requires type-approval by the energy Authority and/or by the utility, to
comply with the grid: deliver power (with a fair share of reactive power) in the time-shift when the
grid indeed needs power; as a clean 50 Hz sinewave free of harmonics; with safety provisions, etc.
This solution is shown in drawing B.
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3.3.3 Advantageous Effects
With a small additional investment (and a loss in the order of 5% due to one additional storage step)
a tremendous gain in flexibility in the use of the electric car for daily trips.
3.4 Description of Drawings
See the description given above.
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3.5 Possible Implementation
The implementation is straightforward according to the description given above. Development,
type-approval and series manufacturing is affordable even to SMEs; nevertheless it will require
(exclusive or non-exclusive, as the cse may be) non-disclosure agreement for secure exchange of
proprietary data, and a co-operation agreement, with the main manufacturers of electric cars, in
order to safeguard the onboard battery as it deserves, and avoid breaching the warranty. Dealings
with large industrial groups like car manufacturers requires something more that just technical skill:
and to this purpose, a patent is an essential step.
Utmost attention shall be paid to safety.
We deliberately disregard the specific choice of one or another technology for the stationary battery.
Lead-acid could be taken as a budgetary reference, however bearing in mind that at least in terms of
safety it is not optimal, owing to release of gaseous H 2 during charge, which requires ventilation
(mainly an exhaust at ceiling level): not easily available when HAFSCEC is installed in a basement.
Apart from H2, the high amount of energy stored in whatever type of stationary battery raises some
concerns about fire in case of severe hit to the enclosure, as may occur when maneouvering a car.
Likewise, the battery voltage (to be optimised, but anyway in the order of a few hundred Volts) is
hazardous to persons, and cannot be easily “switched off”, therefore multiple physical protection
layers shall be provided to avoid direct contact. Last but not least, measures shall be taken against
leakage of corrosive or toxic liquids (e.g. sulphuric acid) should the battery container be damaged.
Similar requirements apply already to the onboard battery – we just have to apply them wisely.
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3.6 Industrial Applicability
The industrial application of the device is quite straightforward and affordable to any SME that is
fluent in multidisciplinary application including a mix of digital, analogue, and power hardware and
software, RAMS (reliability, availability, maintainability and safety), human factors engineering, …
No major technology breakthough is required: the inventive step and the added value mainly lie in a
clever integration of technologies available today. Instead, we foresee “industrial research” and
“experimental development”, as conventionally defined within the EU for the purposes of granting
State aids, followed by manufacturing of a representative prototype for field test and type-approval.
Manufacturing in small series is also affordable to SMEs: the market is typically B2B, and does not
require a capillary sales network.
Special attention shall be paid to the “perennity” of the system. Once type-approved, it shall not be
subject to obsolescence just due to the onset of new releases by software operating systems vendors,
new ICT standards and new devices that implement them and take over existing ones. Regarding
software, this speaks in favour of open sources. Regarding hardware, this will require a wise choice
of electrical, electronic and electro-mechanical (EEE)-parts, as usual in Aero-Space and Defence,
avoiding unique sources and devices that are subject to export constraints from the manufacturer’s
countries (EAR/ITAR).
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4 Claims
Claims are itemised hereafter: by cardinal numbers (independent), respectively letters (dependent):
Claim 1 : that the device uses a stationary battery as a buffer, that all day long stores energy from
the mains at low power (e.g. 3kW) in compliance with a typical household contract with the
utility, and then delivers this energy to the car’s onboard battery in the shortest time possible
(only depending on the onboard battery’s technology);
jointly and severally with the following dependent claims:
a: that in case the household also includes renewable energy sources (PV or windmill)
the same stationary battery (see Claim 1) can store their energy while it is available,
and then deliver it to other household appliances as and when it is required, or return
it to the grid, in order to smooth the respective offer and demand peaks;
Claim 2 : that the device includes a mains current monitor (either a shunt inserted downstream of
the household meter, or a current clamp) to measure the power demand by other appliances;
jointly and severally with the following dependent claims:
b: that the current monitor in Claim 2 also measures the phase of current vs. voltage;
Claim 3 : that the device includes a smart power converter;
jointly and severally with the following dependent claims:
c: that the converter (see Claim 3) based on the measure of power demanded by other
appliances (see Claim 2) adjusts in real time the instantaneous power it drains for its
primary functions (see Claim 1) to fit within the overall power envelope (e.g. 3kW)
available for that household;
d: that the converter is aware of the different (e.g day- vs. night-time) tariffs profile
applied by the utility;
e: that the converter can be programmed by the user, and/or has a “learning” function,
whereby it builds a time profile of the demand of electricity within that household;
f: that, further to Claims d and e, the converter optimises its own use of mains power
according to the time profile of tariffs and demands;
g: that, in case the household also includes renewable energy sources (PV or windmill),
the converter (see Claim 3) can be programmed by the user, and/or has a “learning”
function, and/or can get information from the web (e.g. weather report), whereby it
builds a forecast of the power offer from the household’s own renewable sources, vs.
power demands from the grid;
h: that, further to Claim g, and without harm to its primary function per Claim 1, the
converter optimises the use of the stationary battery as a buffer between power offer
from the household’s own renewable sources, and power demands from the grid;
i: that, further to Claims b and h, the converter deliver the optimal amount of reactive
power that compensates, locally within the household, the reactive power required by
heavily inductive appliances;
Claim 4 : that the device, if installed in series with the other appliances (first case under Claim 2)
includes a manual override pushbutton, that turns off other household appliances, and sets
aside the full power from the mains (e.g. flat 3kW) until the battery is fully charged;
jointly and severally with the following dependent claims:
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j: that, further to Claim 4, the converter implements a hierarchy of appliances, with at
least two levels (essential, e.g. lighting, vs. un-essential, e.g. washing machine) for
household safeguard.
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5 Non-Claims
For further avoidance of doubt we hereafter itemise the main existing technologies exploited here,
that individually considered as such, are not the subject of our claims:
6 Drawings
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