GB2579879A

GB2579879A - Energy-efficient, self-contained welfare cabin

Info

Publication number: GB2579879A
Application number: GB1913993.0A
Authority: GB
Inventors: Wild Ian
Original assignee: Boss Cabins Ltd
Current assignee: Boss Cabins Ltd
Priority date: 2018-09-28
Filing date: 2019-09-27
Publication date: 2020-07-08
Anticipated expiration: 2039-09-27
Also published as: GB201913993D0; GB2587850B; GB2587850A; GB2579879B; GB202008902D0

Abstract

A self-contained water closet cabin is disclosed comprising a fuel-based generator set, a renewable energy generator and an electrical system having an energy store arranged to be charged by the renewable energy generator. The electrical system has and a number of selectively activatable electrical appliances comprising one or more light, an electric water heater, and an air heater. The electrical system further has a controller arranged to monitor the level of charge of the energy store and a power requirement of one or more of the electrical appliances concurrently activated The controller selectively initiates operation of the generator set according to said power requirement. The maximum power output of the generator set is less than the combined power demands of the appliances and the controller is arranged to deny power supply to at least one of the appliances in accordance with a predetermined hierarchy if the combined power output of the renewable generator and the generator set is less than the combined power demands of the appliances. The renewable generator may be a solar panel, the generator set may be an internal combustion generator or may be a fuel cell.

Description

Title -Energy-Efficient, Self-Contained Welfare Cabin

INTRODUCTION

The present invention relates to self-contained, free standing welfare cabins, such as water closets. Such cabins are often used in remote locations or worksites where mains power and/or sewerage connections are unavailable.

Traditionally welfare cabins are supplied with an integral generator set, i.e. a diesel engine generator, to supply off-grid power to electrical appliances within the cabin. It is a typical requirement of conventional generator sets that they are sufficiently powerful to run all of the internal appliances of the welfare cabin simultaneously. The downside of this is that running all the appliances simultaneously does not occur frequently, or for long periods, so the diesel engine of the generator set can be run close to idle for a significant portion of its operation.

This type of operation represents an inefficient use of the engine, thereby incurring unwanted fuel consumption and increasing engine wear.

If diesel engines are run at either low speeds or low loads, for example when a generator set is left idling as a so-called "standby" generator, or when a low load is applied to a higher-capacity generator set, then incomplete combustion of the fuel can occur, leading to carbon fouling or 'coking' issues. Incomplete combustion of the fuel leads to carbon formation in the engine, which is detrimental to engine efficiency and which in turn damages engine components, such as injectors, piston rings, as well as the seals that the piston rings form.

As well as carbon build-up itself, coking can cause further resulting problems with engine operation. For example, as a result of the decreased sealing capacity caused by coking damage, hot combustion gases can reach, and thereby ignite, oil in the system (often indicated by the engine producing blue smoke), which reduces the amount of oil present for lubrication purposes. In addition, incomplete combustion of the fuel may cause the formation of acids in the engine oil, which may cause further damage to the engine components over time.

Such issues, amongst others, increase the likelihood of engine faults and require the engine to be serviced on a regular basis, which thereby increases the maintenance costs associated with self-contained cabins. Such costs can contribute to a significant proportion of the overall costs of operating a self-contained water closet.

European Patent EP 1 716 298 discloses further perceived problems with the use of diesel generators in self-contained cabins, such as noise, fuel consumption and exhaust fumes. As a solution EP 1 716 298 proposes a self-contained lavatory cabin with a solar panel to power electric lights and a burner and heat-exchanger arrangement for air heating in the cabin. The hot air can be used for heating the cabin interior, for a hot air dryer and to heat water for storage in a hot water tank.

Simple controls are enabled using an air temperature sensor and an infra-red sensor to detect a person within the cabin. The lights and other electrical components are activated in a stand-by mode when a person is present and air heating is initiated if the internal cabin temperature is below a threshold temperature.

However there are numerous cabin usage scenarios in which a relatively high energy consumption by the cabin is required, for example on a busy work site or at an event. In such scenarios, a solar powered cabin can fail to meet the energy demand and any onboard batteries can become drained quickly.

It is an aim of the invention to provide an improved self-contained cabin that resolves or mitigates one more of the above identified problems.

STATEMENTS OF INVENTION

There has now been devised a self-contained water closet and an associated control system, which employs a generator set in an efficient and sustainable manner so as to increase the servicing/maintenance interval.

According to a first aspect of the present invention there is provided a self-contained welfare cabin comprising a fuel-based generator set (i.e. electrical power is generated by combustion/oxidation of a consumable fuel), a renewable energy generator, an electrical system having an energy store arranged to be charged by the renewable energy generator and a plurality of selectively activatable electrical appliances comprising: one or more light; an electric water heater; and, an air heater, the electrical system further comprising a controller arranged to monitor the level of charge of the energy store and the summation of a power requirement of the plurality of electrical appliances concurrently activated, wherein in the event that said power requirement is greater than a power output threshold of the energy store, said controller selectively initiates operation of the generator set.

The power output of the generator set, e.g. the max power output, may be less than summation of the power requirements of all the electrical appliances.

If the power requirement of the concurrently activated electrical appliances exceeds the output of the generator set, the controller may deny power supply to at least one of said appliances according to a predetermined appliance hierarchy. Additionally or alternatively, the controller may meet the power requirement by a combination of power supply from the generator set and the renewable energy generator and/or energy store.

The power output threshold may comprise a level of charge and/or rate of discharge of the energy store.

The controller may additionally monitor the power output of the renewable energy 20 generator.

The plurality of electrical appliances may be individually connectable to the generator set and/or energy store to draw power concurrently therefrom.

The invention may permit efficient fuel consumption by the generator set, e.g. over prolonged use. The invention may enable the generator set used to have a lower maximum power threshold, as the generator set does not need to cope with the combined total electrical power demand for concurrent use of all electrical appliances. The maximum power threshold of the generator set may be less than the summation of the power requirements for all the electrical appliances of the system, e.g. being less than or equal to the summation of the power requirements of all-but-one, all-but-two, or fewer of the electrical appliances.

The use of a generator set having a lower maximum power threshold may be advantageous as this may prevent or reduce low-loading of the generator set. The invention may therefore result in lower levels of carbon build-up or associated problems in the generator set, which may increase servicing intervals, improve fuel consumption, and/or lead to decreased running costs. A smaller, more cost-efficient engine capacity may be used.

The controller may be configured to selectively control the electrical power supplied by the generator set to the appliances based on a prioritisation algorithm, for example a preprogrammed prioritisation algorithm. The prioritisation algorithm may determine which of the electrical appliances is supplied with electrical power when the total electrical power required for concurrent use of the activated appliances exceeds a maximum electrical power output threshold of the generator set.

The appliance hierarchy and/or prioritisation algorithm may be determined at least in part by the electrical power consumption of the electrical appliances, e.g. a current/instantaneous, maximum or average power consumption value.

Each of the plurality of electrical appliances may be logged as higher priority or lower priority relative to the other electrical appliance(s) within the hierarchy.

Upon activation of a higher priority appliance by a user, the controller may be configured to switch or restore the supply of electrical power from an activated lower priority appliance to the higher priority appliance. The controller may switch supply of electrical power from a higher priority appliance to an activated lower priority appliance, for example after a pre-determined time period of use of the higher priority appliance has elapsed, or when the operation of the higher priority appliance has ceased.

The controller may comprise a control circuit and one or more switches under control of the control circuit. A plurality of electrical switches may be provided for selectively connecting/disconnecting each appliance to the generator set and/or energy store by the control circuit.

The controller may iteratively deny power to the next lowest priority appliance of the activated appliances until the power output threshold is met.

The controller may be configured to output a signal indicating when an activated appliance is denied power. The controller may be configured to output a signal indicative of which of the activated electrical appliances is being currently supplied and/or denied electrical power from the generator. The signal may, for example, comprise any or any combination of an electrical/data signal, an audio signal, and/or a visual signal.

The electrical appliances may comprise a water pump.

The light(s) may be connected to the generator set via the electrical energy store. The light(s) may be powered by the energy store, e.g. only by the energy store.

The light(s) may have a different/lower power rating to one or more of the (other) electrical appliances.

The electrical power threshold of the generator set may comprise at least 1 kW, at least 2kW, or at least 3kW. The electrical power threshold of the generator set may comprise at most 3kW, at most 4kW, at most 5kW, at most 6kW, at most 7kW, at most 8kW, at most 9kW, or at most 10kW. In the example of a fuel cell generator, the electrical power threshold may be lower, e.g. in the order of 200-500 watts or 500-1000 watts.

The controller may be configured to automatically begin operation of the generator set when minimum power requirement threshold or minimum generator output threshold is met. The controller may be configured to automatically cease operation of the generator set where no electrical loads are in use or else when the power requirement of the activated appliance(s) fails to meet a minimum power threshold.

The controller may control selective charging of the energy store by the generator set. The controller may control selective discharging from the energy store to one or more active appliance. The controller may meet some or all of the power requirement of the activated device(s) from the energy store in addition to, or instead of, via the generator set.

The controller may selectively charge the energy store, e.g. in combination with supplying power to one or more other activated appliance. The controller may selective charge the energy store to ensure a minimum power output threshold or desired operating point of the generator set is met.

The fuel-based generator may comprise a fuel cell, e.g. cell for use with a hydrogen or methanol fuel.

The fuel-based generator may comprise a combustion engine, e.g. a diesel or petrol engine.

The fuel-based generator may be connected to a self-contained fuel supply, such as a fuel tank. The fuel may be gaseous and/or liquid.

The engine of the generator set may be operated at a desired operating point, e.g. in a substantially steady state, or else within a predetermined range of variation of said desired operating point. Variation in engine operation over its full operational range may be inhibited or restricted. The engine may be operated only at a fixed operating point or range, e.g. as defined by a torque output, throttle or rotational speed setting.

The hierarchy may comprise a ranking from 1 to n (where n is the number of electrical appliances connected to the generator set).

Any or any combination of the electrical appliances may have associated therewith a predetermined or pre-set duration of operation. The predetermined duration of operation may comprise a known maximum duration of an instance of operation of the appliance. The pre-set duration may comprise a duration of a current instance of activation set by a user.

The electrical system may comprise one or more sensor. The controller may permit or deny power to one or more electrical appliance based on the output of said one or more sensor. The sensor may comprise any or any combination of: a proximity/movement sensor, a water temperature sensor, an air temperature sensor, a light sensor, a flow sensor and/or a closure actuation sensor.

The electrical system may comprise DC and AC circuits. One or more electrical appliance may be on the AC circuit, e.g. the water and/or air heater. One or more further electrical appliance may be on the DC circuit, e.g. powered via the energy store.

The electrical system may comprise an AC to DC converter, e.g. connecting the generator set to the energy store. The electrical system may comprise an inverter, e.g. for powering the AC circuit from the energy store.

The water closet may comprise a transparent roof or portion thereof, such as a panel.

According to a second aspect of the invention there is provided: a self-contained welfare cabin comprising a fuel-based generator set, an electrical system having an energy store arranged to be charged by the generator and a plurality of selectively activatable electrical appliances comprising: one or more light; an electric water heater; and, an air heater, the electrical system further comprising a controller arranged to monitor the level of charge of the energy store and the summation of a power requirement of the plurality of electrical appliances concurrently activated, wherein in the event that said power requirement is greater than a power output threshold of the energy store, said controller selectively initiates operation of the generator set.

The fuel-based generator may comprise one or more of a fuel cell or a combustion engine.

According to a third aspect of the present invention there is provided a self-contained water closet or welfare cabin comprising a combustion engine generator set, a fuel cell generator set, an electrical system having an energy store arranged to be charged by the fuel cell generator set and a plurality of selectively activatable electrical appliances comprising: one or more light; an electric water heater; and, an air heater, the electrical system further comprising a controller arranged to monitor the level of charge of the energy store and the summation of a power requirement of the plurality of electrical appliances concurrently activated, wherein in the event that said power requirement is greater than a power output threshold of the energy store, said controller selectively initiates operation of the combustion engine generator set.

Any of the optional features disclosed in relation to the first aspect may be applied to any further aspect of the invention.

DETAILED DESCRIPTION

Practicable embodiments of the invention are described in further detail below with reference to the accompanying drawings, of which: Figure 1 shows a schematic above/plan view of a free-standing water closet in accordance with an example of the invention; and, Figure 2 is a schematic block diagram illustrating a water closet electrical/control system according to an example of the present invention.

The invention focuses on providing a water closet cabin with efficient methods of water heating, personnel heating and lighting such that the energy use for the cabin is kept to a minimum, whilst also allowing a long service interval. The cabin has been developed to give people energy efficient toilet facilities in remote areas where there is no available mains power and/or sewerage connections.

A free-standing water closet (WC) cabin according to an example of the present invention is shown schematically in Figure 1 and generally designated 10. The water closet can be located anywhere it is needed without connection to water or electricity mains.

The WC comprises an outer wall 12 around its perimeter and inner dividing wall 14, which separates the user compartment 16 from an equipment compartment 20. The outer wall 12 provides for a rigid container that is resilient to vandalism. The outer wall may comprise one or more vents 15 to the cabin exterior in any, any combination or all of the internal compartments.

In this example, the WC 10 comprises two user compartments 16 and 18 in a side by side configuration, e.g. separated by a further internal dividing wall 22. However in other examples, a single user compartment 16 can be provided if required. The unit could have further user compartments if desired, e.g. in the form of a larger welfare cabin. Such other compartments could comprise a seating area and/or kitchenette/galley in addition to the toilet facilities disclosed herein.

Each of the user compartments 16, 18 and equipment compartment 20 is provided with a door 24 that opens to the exterior of the WC cabin 10. The doors 24 each have locks 26 and are designed to be difficult to break into by way of their fitment into the corresponding frame in the outer wall 12, as well as by the nature of the lock 26.

The user compartment 18 may be a copy of the user compartment 16 and so the details of that compartment are not duplicated for simplicity. In other examples, the compartment 18 could comprise a washing compartment, e.g. instead of a WC compartment.

The user compartment 16 comprises a sink 28 with a tap 30 to provide hot or cold water and a toilet 32.

The compartment may additionally comprise a urinal 34. The urinal 34 in this example comprises a waterless urinal such that it does not have a connection to a fresh water tank for cleaning/flushing. Instead the urinal has an outlet pipe connected to a waste tank and may comprise a valve in the outlet pipe, e.g. a one-way/non-return valve that is biased to a closed condition and openable by liquid thereon.

Electrical components within the user compartment comprise a light 36, personnel sensor 38 and an air heater 40. The personnel sensor 38 can be provided within the light module in this example but could otherwise be provided as a separate component if desired. The personnel sensor 38 typically comprises a proximity sensor and/or movement sensor of a known type.

An additional sensor 42 is provided in the cabin in the form of a light sensor. The light sensor senses the level of ambient light within the compartment 16.

In addition to the sensors described above, a door sensor could be used to detect entry/exit to the compartment. The use of the various sensors is described below with reference to the electrical system.

The air heater 40 may comprise one or more infra-red heating panel (i.e. a radiative heating panel) but could additionally or alternatively comprise an electrical fan heater of conventional type or another convective heater.

A skylight 44 (shown in phantom) is provided in the roof of the compartment 16 so as to allow entry of ambient light into the compartment interior. The skylight is typically formed as a panel of transparent or translucent material mounted across an opening in the cabin roof. In other examples, the skylight could be provided in the upper region of the outer wall 12 of the cabin if desired.

In this example, the skylight 44 spans the user compartment 16 and equipment compartment 20.

A solar panel 46 (shown in phantom) is mounted on the roof of the WC cabin 10. The solar panel is mounted adjacent the skylight 44 in this example, e.g. between two skylights. One or more solar panel may be provided depending on the available area for mounting. In other examples, the solar panel(s) could additionally or alternatively be fitted to the side of the outer wall 12.

One or more external light 47 is provided on the external side of the outer wall 20 or roof. The external light 47 may have a proximity/movement sensor. Alternatively, the external sensor could be provided separately.

The equipment compartment 20 houses the following: - A generator set 48; - An electrical energy store 50, e.g. in the form of a battery or battery bank; - A fresh water tank 52; -A waste water tank 54 - A water pump 56; - A water heater 58; and - An electrical control system 60.

Whilst the waste water tank 52 is described as being within the equipment compartment 20, it could be located beneath a floor of the WC, e.g. beneath the user and/or equipment compartment.

The generator set 48 comprises a fuel-based generator configured to consume/combust/oxidise a consumable fuel to generate electrical power. The generator set 48 is operatively connected to a fuel supply, for example, a self-contained fuel supply, such as a fuel tank or a pressure cylinder.

In some embodiments, the generator set 48 is a combustion engine generator. For example, the generator set 48 comprises a conventional diesel generator set, and in some embodiments may comprise a diesel engine having an output shaft which drives a rotor of an electrical generator. The electrical generator and motor are typically co-located and/or mounted to a common support structure, such as a chassis/frame.

Additionally or alternatively, the generator set 48 may comprise a fuel cell 49. The fuel cell is configured to oxidise a fuel to generate electrical power (i.e. in a direct fashion). For example, the fuel may comprise hydrogen, carbon monoxide, methane, methanol or other conventional fuel cell fuels. The fuel cell 49 may provide a low power output (e.g. less than the engine generator). In different examples, the fuel cell 49 may be provided as an alternative to the combustion engine generator set, or else the renewable engine generator.

The electrical control system 60 comprises a controller provided as one or more processor or logic circuit in communication with the sensors described herein and arranged to output control signals to the various electrical components of the electrical system. The control system 60 is referred to as an intelligent load management system.

The electrical control system may also comprise a fuse box, e.g. comprising one or more conventional fuse/trip-switch for selectively denying power to one or more electrical components, e.g. in response to an electrical fault. The control system may further comprise a set of electrical switches under the control of the controller, e.g. switches for each electrical circuit connected to the electrical system.

The electrical control system also comprises one or more power converter as described below.

An overview of the electrical system is shown in Figure 2. The electrical system comprises AC and DC systems/circuits. The AC system is designated by the boundary 62 and comprises the AC generator 48 and an AC-DC converter (e.g. rectifier) 64 that may be provided as part of a battery charger. The AC system also comprises one or more air heater 40.

Where present, the fuel cell 49 may form part of the DC system (i.e. the generator set 48 or a portion thereof is operatively connected to the DC system).

The AC system may be a 230V system and the DC system may be a 12V system. However alternative voltages may be provided to suit local requirements in different countries, e.g. on the understanding that the DC system will be of lower power rating than the AC system.

A DC-AC converter/inverter may also be provided as part of the power control system. In some embodiments, an inverter may be used to covert DC power from the fuel cell 49 to provide power to the AC system.

A water heater 58 may be provided on the AC circuit and/or DC circuit. In this example both an AC and DC water heaters are provided and the controller 60 can switch either/both on off as required. Those water heaters may allow for different power output, e.g. to permit different rates of heating such as instant and/or longer term hot water heating for a hot water tank. In this regard, the cabin 10 may comprise a hot water tank, i.e. separate to the fresh water tank 52.

Although not shown in the figures, it will be appreciated that a hot water tank, or instant hot water heating system, will comprise a water temperature sensor in communication with the controller 60. The current temperature reading can be used to determine whether the water temperature is acceptable (i.e. to prevent overheating and/or to alter the priority of water heating within the control logic).

The solar panel 46 and battery bank 50 are connected to the DC circuit. The DC output of the solar panel 46 can thus be used to charge the battery 50 via a battery charger 66. The battery charger 66 may comprise a charge controller, e.g. to monitor the level of charge on the battery and selectively disconnect the battery when a maximum charge level is reached. The battery charger 66 may optionally comprise a DC-to-DC converter/regulator.

The appliances connected to the battery on the DC circuit comprise: the interior 36 and/or exterior 47 light(s); the water pump 56; and, optionally, a DC water heater.

In the example of Figure 2, each of the lighting and space/air heating appliances are controlled at least in part in accordance with the output of the one or more motion/proximity sensor 46. Each appliance is shown in Figure 2 schematically as being connected to the system via a PID sensor.

In use, the power for the DC system is stored in the batteries 50, which are charged up predominantly by the solar panel(s) 46 fitted to the roof or side of the WC cabin 10.

The control system 60 monitors and manages the battery charge level and if insufficient charge is created from the wind or solar sources then the batteries 50 are topped up with power from the generator 48 via the charger 64 (or charger 66 for the fuel cell 49). If the battery charge level drops below a certain level (i.e. a minimum threshold) the generator will automatically start and run until the batteries are sufficiently/fully charged.

The fuel cell 49 may be used to trickle charge the battery, due to the relatively low power output of the fuel cell. This allows the battery to be charged without stressing and/or overheating the battery. The fuel cell 49 may be used to charge the battery in addition to or in lieu of the renewable energy generator 46. Where the charging power of the fuel cell is not sufficient, the combustion engine generator may be used in addition to or in lieu of the fuel cell.

In some examples, e.g. in systems where fewer or lower-power electrical appliances are used, the diesel generator set could be negated altogether and the system may comprise only the fuel cell and renewable energy generator. The fuel cell could provide relatively constant background charging of the battery up to a threshold level of charge on the battery, e.g. to accommodate the peaks and troughs of renewable energy generation.

The batteries may additionally/alternatively be fitted with a load shedder so that if for any reason the battery charge level drops too low the load is switched off by the controller 60 to prevent the batteries being deep discharged. This could happen e.g. overnight or when there is insufficient solar power, and no fuel for the generator to work, or a generator failure.

The AC power is provided through the use of a small diesel generator 48 so that fuel usage is kept as low as possible. This will result in the generator being unable to power all the connected AC appliances concurrently (i.e. the space heater(s) 40, water heater 56 and/or battery charger 64. The generator is managed with an intelligent load management system that is configured so that when more appliances are being asked to run than there is available power for then the appliances will be supplied power in order of a specified priority as will be described below.

An electric heated water storage tank is fitted, this provides the hot water for the hand wash sink(s) 28. The sink 28 is fitted with non-concussive taps 30 so that water usage is kept to a minimum. The hot water tank is managed by the controller 60 so that it is kept topped up and only heated when necessary. A water level and/or temperature sensor may be provided in communication with the controller 60 for this purpose. The control system may be configured to prevent frost damage, e.g. by monitoring water temperature against a minimum threshold temperature (i.e. above freezing) and using a small amount of power to maintain a temperature within the water system.

The pressure for the water taps may be provided by an accumulator to store pressure.

When the pressure drops the control system 60 will run the water pump 56 until the pressure reaches the desired level. A water pressure sensor may be provided in communication with the controller 60 for this purpose.

The toilet 32 flush system is designed to only use a small amount of water per flush. This reduces the waste tank 54 capacity required to prolong the duration between service visits to empty the tank.

The water pump 56 will only run when required by the toilet flush or to top up the water tank or accumulator.

The lighting inside the cabin is 12V LED lighting consuming minimal power, it is controlled so that it only illuminates when there is someone present (according to the output of sensor 38 or a door opening sensor) and there is insufficient natural light (according to a comparison of the output of sensor 42 with a minimum threshold value of ambient light).

The control system may also switch off the internal light after a set time of operation to conserve energy, e.g. a period for which the presence of a person within the cabin is not detected.

Natural light is provided inside through the use of the skylights described above. This eliminates the need for internal electric lighting during most daylight hours.

The external lighting is 12V LED lighting consuming minimal power, it is controlled so that it only illuminates when there is someone present and there is insufficient natural light (i.e. determined according to the relevant sensor outputs in a manner akin to the internal lighting control). The control system also turns it off after a set time to conserve energy.

Personnel/space heating is controlled so that it only operates when the ambient temperature is below a predetermined threshold and someone is present. Thus an ambient temperature sensor may be provided inside the WC and may be used by the control system in conjunction with one or more personnel sensor described herein to control operation of the heater 40 automatically. The heating will turn off once there is no longer anyone present in the cabin. The heating can be 12V or 230V, if the heating is 230V the power could be provided from the 12V batteries via an inverter for a more-limited period of time but will often require start-up of the generator. The heating is preferably provided by an electric, resistive element (e.g. including a fan) heater or infra-red heating panels.

The battery 50 may be charged via either or both of the generator and solar panel 46. A charge on the battery may be used to power the system, in addition to, or instead of, the generator set 48. Thus the system can operate for a period of time via the battery(s) 50 alone when the generator set 48 is not in operation or fails, or else when the generator set output is insufficient to meet the demands of the devices drawing power from the system. The lighting and water pump can be powered directly from the battery 50 in particular to ensure basic needs are met as a priority.

The controller 60 comprises a microprocessor, such as a programmable circuit board or programmable logic device. The controller 60 in presently preferred embodiments is preprogrammed with a prioritisation algorithm which dictates a preferential supply of power to certain appliances over others.

Each electrical load/appliance may thus be given a ranking of 1-n, where 'n' is the number of electrical appliances connected to the electrical system. Using this technique, each appliance has a ranking that can be used to determine which appliance(s) should be powered in the event that it is not possible to supply instantaneous power to meet all the electrical loads on the system. However the interior lighting, exterior lighting and water pump are run from the battery and can collectively be accommodated by measuring the charge on the battery, e.g. rather than, or as well as, the power drawn by each individual appliance.

Therefore only the 230V/AC appliances may need to be managed by the controller in the following order of priority: - energy store charging - air/space heating - water heating.

The controller 60 comprises one or more routine/algorithm to determine whether or not to activate the generator set 48. In a simple example, this may involve monitoring a current level of charge on the battery 50 and activating the generator set whenever the charge on the battery 50 drops below a minimum threshold. The generator may additionally or alternatively be activated whenever the controller determines that a heater, such as heater or 58 is to be activated, i.e. according to the relevant sensor signal inputs.

The control system may supply any or any combination of the aforementioned electrical loads with power provided that the maximum power threshold of the generator set 48 is not reached. If the maximum power threshold of the generator set is reached the controller may optionally check the charge level on the battery and/or the instantaneous power supplied by the solar panel 46 to determine whether the demands of the concurrent electrical loads on the system can be met by the combined power supplied by the generator 48 and solar panel 46.

Where the maximum power threshold of the generator set (optionally including the power supplied by the solar panel) is reached, the controller 60 will operate to remove supply of electrical power to one or more of the electrical loads until the electrical power in use by the electrical loads is lower than the maximum power threshold.

Operation of the welfare cabin control system in such a manner means that the power threshold of the generator set 48 only has to be large enough to enable operation of the electrical load having the largest maximum power rating, as concurrent operation of any combination of electrical loads resulting in a total power rating greater than the maximum power threshold of the cabin will result in operation of the controller 60 to selectively remove and/or switch supply of power to the electrical loads until the total power rating of the electrical loads in concurrent use is achievable.

The controller 60 may also monitor the current rate of charge on the battery and the current rate of discharge from the battery to meet the electrical demands of the connected appliances. Thus rather than monitoring the solar panel output per se, the controller 60 could simply monitor the charge level on the battery and/or the rate of charge/discharge from the battery. In this regard, the controller may only need to receive the relevant sensor inputs (being indicative the appliances to be activated) and the level of charge on the battery in order to decide whether or not to activate the generator set and also the priority order of the appliances to be powered.

This provides a simple but highly effective and efficient control strategy.

The exact maximum power threshold of the engine generator set relative to the total/collective power requirement of all electrical loads on the system may be selected so as to ensure that the motor is normally operating at a non-idle throttle/rpm setting when in use. This may be determined by analysing normal variation in power usage and selecting a generator set for which a desirable operational range of the motor (i.e. an operational range between idle and a maximum throttle/rpm setting for the engine) at which the engine can operate for prolonged periods without substantial issues arising due to incomplete combustion or coking.

In the present example, instead of defining a desirable range of engine operation, the engine generator set is controlled to operate at a fixed operating point. In a specific example, the engine will run at 3000 rpm. Whether a fixed operating point or defined sub-range of the available engine operating range is defined, the operation is closer to a steady-state and/or optimal efficiency point for the engine. This can carry significant efficiency and/or other practical benefits for the engine.

In some examples, the controller may not have a minimum power threshold, e.g. such that the generator set is always started when an electrical load (e.g. a heating demand) is applied to the system. In other examples, a minimum power threshold may be used to ensure that the generator set is not used for prolonged periods of time below the minimum power threshold. For example the controller may inhibit operation of the generator set when the electrical load on the system is below the minimum threshold and/or may initiate electrical supply to one or more additional appliances (e.g. to charge the battery in addition to the activated appliances) to ensure that the minimum power threshold is achieved. In this regard, the controller may select to supply power to the battery charger 64 at a rate sufficient to meet the minimum power threshold.

When only one or more appliance is required (e.g. lighting/pumping) that does not meet the minimum threshold and the appliance(s) could be powered by the battery 50 alone, i.e. when the battery has sufficient charge, the controller may avoid starting up the generator set and may meet the demand using the battery only. The solar panel is helpful in such scenarios to gradually top up the charge level on the battery between instances of use. If excess power is generated by the solar panel (i.e. the battery is already at full charge) the hot water tank may be pre-emptively heated.

In any examples of the invention, the battery or other electrical energy store may comprise one or more sensor indicating the current level of charge and/or available capacity for energy storage. The sensor output is communicated to the controller such that it can be accommodated in power supply decisions made by the controller.

In further developments of the above system, the controller 60 may be programmable to recurring schedules or other predictable or cyclic events/behaviour. For example schedules may be used to follow trends in energy consumption and/or renewable energy availability. Daily, weekly, monthly and/or seasonal schedules may be used. For example, it may be assumed that the cabin may not be used overnight or at weekends in some instances of use and so a low level of charge on the battery may be sufficient. However scheduling of energy consumption may imply that high levels of energy consumption are expected during the working hours of a morning/afternoon. As such the solar panel may be sufficient to top up the battery over a weekend, implying that the generator set is not required to be used merely because a low charge level exists on the battery at a the start of a weekend.

Also, daylight hours and/or weather forecasts (indications of renewable energy availability) may be used to indicate when renewable energy may be sufficient to meet demands in advance.

Use of scheduling of energy consumption and/or renewable energy availability may further increase the efficiency of the system. Scheduling may be pre-programmed at least in part, e.g. requiring an operator to input the intended days/hours of cabin usage on site to set the system and/or relying on predictable environmental data such as daylight hours and/or ambient temperature. Additionally or alternatively, scheduling may be adaptive, e.g. based on records of energy consumption and/or environmental data in a preceding usage period.

It has been found that power supply systems of the kind described herein can offer generator/energy efficiency savings compared to conventional generator-driven power supply systems. Furthermore the system can better accommodate the peaks and troughs in power consumption better than an renewable-energy-only solution and can allow prolonged maintenance intervals.

The use of fuel cell provides a quiet and low maintenance source of the electrical power. The fuel cell allows the use of renewable and/or clean fuels (e.g. which only exhaust water). Additionally, the fuel cell provides a low power output to allow trickle charging of the battery.

Whilst the above description refers to a solar panel as providing a renewable energy source, it will be appreciated that other renewable energy sources can additionally or alternatively be used, including for example a wind turbine or water wheel. Depending on the renewable power supply, additional or alternative power converter means may be implemented as would be understood by the person skilled in the art.

Claims

Claims: 1. A self-contained water closet cabin comprising: a fuel-based generator set; a renewable energy generator; an electrical system having an energy store arranged to be charged by the renewable energy generator and a plurality of selectively activatable electrical appliances comprising one or more light, an electric water heater, and an air heater; the electrical system further comprising a controller arranged to monitor the level of charge of the energy store and a power demand of one or more of the plurality of electrical appliances, wherein said controller selectively initiates operation of the generator set according to said power demand.
2. A water closet cabin according to claim 1, wherein the maximum power output of the generator set is less than summation of the power requirements of all the electrical appliances on the electrical system and the power demand is a current or predicted power demand of the electrical appliances.
3. A water closet cabin according to claim 2, wherein if the power demand of concurrently activated electrical appliances exceeds the output of the generator set and renewable energy generator, the controller is arranged to selectively deny power supply to at least one of said appliances according to a predetermined appliance hierarchy.
4. A water closet cabin according to claim 3, wherein the controller is arranged to selectively disconnect the lowest priority appliance of the activated appliances, e.g. iteratively, until a maximum power output threshold for the electrical system is met.
5. A water closet cabin according to claim 2, 3 or 4, wherein the controller meets the power demand of concurrently activated electrical appliances by a combination of power supply from the generator set and the renewable energy generator andior energy store.
6. A water closet cabin according to any preceding claim, wherein the controller supplies the plurality of electrical appliances currently activated via the energy store only if the combined power requirement thereof is below a power output threshold and/or if the level of charge on the energy store is above a predetermined level.
7. A water closet cabin according to claim 6, wherein the controller monitors the rate of charge/discharge of the energy store.
8. A water closet cabin according to any preceding claim, wherein the controller selectively charges the energy store using power supplied by the generator set.
9. A water closet cabin according to any preceding claim, wherein each of the plurality of electrical appliances are individually selectively disconnectable from the generator set and/or energy store under the control of the controller.
10. A water closet cabin according to any preceding claim, wherein the controller comprises one or more switches for selectively connecting/disconnecting each appliance to the generator set and/or energy store by the control circuit.
11. A water closet cabin according to any preceding claim, wherein the plurality of selectively activatable electrical appliances comprises a water pump.
12. A water closet cabin according to claim 11, further comprising a water pressure accumulator driven connected to the pump.
13. A water closet cabin according to any preceding claim, wherein the renewable energy generator comprises a solar panel.
14. A water closet cabin according to any preceding claim, wherein the cabin comprises one or more skylight and an ambient light sensor, the one or more light being operable by the controller only upon the ambient light level sensed by the ambient light sensor is at or below a minimum threshold.
15. A water closet cabin according to any preceding claim, comprising a personnel sensor, wherein the controller permits activation of one or more of the selectively activatable electrical appliances based at least in part upon the output of said personnel 35 sensor.
16. A water closet cabin according to any preceding claim, comprising an air and/or water temperature sensor wherein the controller permits activation of one or more heater based at least in part upon the output of said temperature sensor.
17. A water closet according to any preceding claims, wherein the fuel-based generator comprises a fuel cell.
18. A water closet according to any preceding claims, wherein the fuel-based generator comprises a combustion engine. 10
19. A water closet cabin according to claim 18, wherein the one or more light, the energy store and the renewable energy generator are connected on a DC circuit and the combustion energy generator and one or more heater is connected on an AC circuit, the one or more heater being powered by the combustion engine generator and the one or more light being powered only via the energy store.
20. A water closet cabin according to claims 18 or 19, wherein the combustion engine of the generator set is operated at a desired, fixed operating point in a substantially steady state or else within a predetermined range of variation of said desired operating point.