FR3098890A3 - Pressurized gas tank (s) filling station - Google Patents

Abstract

Station for filling pressurized gas tank (s), in particular hydrogen, comprising a source of compressed gas, a gas transfer line between the source and the tank to be filled, a regulating valve in the transfer line for controlling the flow of gas through said conduit, an electronic regulator for controlling the regulating valve comprising a first microprocessor, characterized in that the electronic regulator comprises a second microprocessor configured to automatically stop the flow of gas when at least one conditions security of a filling parameter is not fulfilled

Description

Pressurized gas tank(s) filling station

The invention relates more particularly to a pressurized gas tank(s) filling station.

Currently the filling of tanks for fuel cell vehicles in a hydrogen filling station is managed by a standard automaton. This automaton, depending on the pressure measurements at the outlet of the station and the ambient temperature, will (according to a predefined filling protocol) control the opening of the outlet valve of the station in order to respect a predefined pressure ramp at the outlet of the station. This automaton also manages the pre-cooling of the gas in order to avoid overheating in the tank and stops filling when a target pressure is reached. In addition, it also controls the starting and stopping of the compressor as well as the opening and closing of the buffer tank valves (for balancing(s) in particular in cascade).

In general and for cost reasons, the automaton can break down or malfunction quite frequently and result in less and less safe filling conditions. With the growing development of the fuel cell vehicle market, the occurrence of breakdowns or malfunctions related to this automaton can happen more and more often. This represents a significant risk for the future development of hydrogen filling stations. Hence the interest of offering an economically viable solution while ensuring a sufficient level of safety for hydrogen filling.

The automatons or electronic controllers currently used to manage all the functions in a hydrogen filling station are of the standard type. These automatons may break down or malfunction more and more often due to the rapid development of fuel cell vehicles in the world. The cost of a secure PLC with the associated sensors is significantly higher than that of a standard PLC.

An object of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

To this end, the filling station for reservoir(s) of pressurized gas, in particular hydrogen, comprises a source of compressed gas, a gas transfer pipe between the source and the reservoir to be filled, a regulating valve in the transfer line for controlling the flow of gas through said line, an electronic regulator controlling the regulator valve comprising a first microprocessor, the electronic regulator comprising a second microprocessor configured to automatically stop the flow of gas when at least one security conditions of a padding parameter is not met.

The invention also relates to a filling method implementing the features mentioned above or below.

The invention may also relate to any alternative device or method comprising any combination of the characteristics above or below within the scope of the claims.

Other features and advantages will appear on reading the description below.

The station includes a safety device for automatically stopping hydrogen filling when certain safety conditions are not met.

The invention relates in particular to a device (microcontroller or microprocessor) capable of sending an automatic gas filling stop signal when filling a fuel cell vehicle if the safety conditions are not met. The safety conditions concern at least one of: the maximum internal wall temperature, the maximum density of this gas inside the vehicle tank. In fact, the maximum internal wall temperature limit for a composite tank is generally 85°C. These data (internal wall temperature and density of the gas in the bottle) are very difficult to measure, especially inside a high-pressure tank. The most adequate way to estimate them is to rely on a physical model (thermodynamics) which will be described a little further down.

It should be noted that the limiting density of the gas in the tank depends on the service pressure of the latter and of course on the nature of the gas. For a vehicle tank operating pressure of 350 barg and for hydrogen, this corresponds to a limit gas density of 24.1 kg/m3. For a vehicle tank operating pressure of 700 barg and also for hydrogen, the gas density limit is 40.2 kg/m3.

The input data of this safety device can be the values resulting from the measurements at the gas inlet in the hose of the transfer pipe for (gas temperature, gas pressure and ambient temperature).

The temperature of the gas is measured for example at the level of the gas leaving the filling station just before the connection hose with the vehicle.

The pressure is measured for example at the same place as the dispensing temperature.

The ambient temperature is measured, for example, at the station.

The safety device or module calculates in real time during filling according to a (known) physical model: the internal wall temperature in the tank of the vehicle as well as the density of the gas inside this tank and checks that the two do not exceed permitted limits (e.g. 85°C, 24.1 kg/m3 or 40.2 kg/m3 depending on tank working pressure 350 barg or 700 barg respectively).

This calculation is done at each time step (of the order of a second for example) and is based on the measurements mentioned above. If at least one temperature or density overrun is detected, the safety module sends an output signal to automatically stop filling the vehicle.

The physical model used by the security module can be based on the known energy balance equations applied to the gas in the tank and to the wall thereof.

This balance can involve the mass of the gas in the tank, the internal mass energy of the gas in this tank, the heat exchange between the gas in the tank and the internal wall of the latter with the exchange coefficient and the internal surface of this tank as well as the incoming mass enthalpy of the gas in the tank. As such, the average spatial temperatures of the gas in the volume of the tank and of the wall thereof can be calculated.

The enthalpy balance equation can be applied to the tank wall.

This balance can involve the mass of the tank wall, its heat capacity and the heat exchange between the external wall of the tank and the ambient environment around the tank with the total exchange coefficient and the external surface of this tank.

By dividing the two preceding balance equations by the volume of the gas in the reservoir and by involving the average density of the gas in the reservoir, two differential equations are obtained.

For example, these differential equations are of order one in time and involve three coefficients which depend on the geometric characteristics and the calorific capacity of the tank as well as the coefficients of exchange between the wall of the tank and the gas in the tank and also that with the surrounding environment.

A coefficient depends on the flow rate of the gas entering the tank which can vary as a function of time through the variation of the convective exchange coefficient between the gas and the internal wall.

The incoming gas flow is highly dependent on the pressure ramp. The greater this ramp, the greater the incoming flow and the greater the exchange coefficient and therefore the coefficient concerned.

Following several detailed tank filling calculations, it can be seen that the second coefficient can be smoothed in polynomial form as a function of the pressure ramp at the inlet to the tank. A polynomial of order two with the pressure ramp is sufficient to express the variation of the second coefficient according to this ramp.

Among the three coefficients considered, only the second coefficient depends on time through the dependence of the pressure ramp with time. To be able to solve the system of nonlinear differential equations, it can be discretized by replacing the time derivatives by finite differences. We thus obtain two discrete equations.

From the numerical discretization of these two balance equations, this model can calculate for each time step the wall temperature of the tank as well as the product density of the gas in the tank and the specific internal energy of the gas and this by based on the three parameter measurements mentioned above and also on the values of the variables at the previous moment.

It should be noted that for a given gas, the specific internal energy, the specific enthalpy as well as the density of the gas are often tabulated according to the pressure and the temperature of the gas or adjusted with known functions of the pressure. and temperature. On the other hand, the initial pressure of the tank is that measured when the filling starts. As for the initial temperature of the gas and the wall of the tank, it is a function of the initial ambient temperature according to the recommendation of the J2601 standard for the filling of fuel cell vehicles.

The gas pressure in the reservoir is assumed to be equal at all times to that measured at the level of the dispenser.

In addition, it is assumed that the gas inlet temperature in the reservoir is equal at all times to that measured at the level of the dispenser.

In order to be able to estimate at each time step the tank wall temperature but also the density of the gas, the model needs to know the geometric characteristics of the vehicle tank. These characteristics are not necessarily transmitted systematically from the vehicle to the station at the time of filling and on the other hand the reliability of this data is not guaranteed. Therefore, the model can consider the most critical tank in terms of wall heating during filling and also the one that maximizes the gas density during filling.

At each time step, the model can calculate the wall temperature using the values at the time before according to the equation concerned. In addition, this model can calculate for each time step the product using the equation concerned and deduce the temperature of the gas in the reservoir according to the following function.

This function can be adjusted according to the thermo-physical properties of the gas which depend on its pressure and temperature. The temperature of the gas at each instant is useful for calculating, among other things, the density function of the gas which appears in the two equations.

The specific enthalpy of gas is also a known function of temperature and pressure.

We can thus calculate the specific enthalpy of the gas entering the bottle which appears in the equation by replacing the temperature and pressure values with those measured at the outlet of the filling station.

So finally the model calculates at each time step the temperature, density and checks if these two values do not exceed the predefined limits. If these two limits are not exceeded, the filling continues. On the other hand, if at least one of the two limits is exceeded, the model sends a signal to stop filling.

Claims (1)

Station for filling pressurized gas tank (s), in particular hydrogen, comprising a source of compressed gas, a gas transfer line between the source and the tank to be filled, a regulating valve in the transfer line for controlling the flow of gas through said conduit, an electronic regulator for controlling the regulating valve comprising a first microprocessor, characterized in that the electronic regulator comprises a second microprocessor configured to automatically stop the flow of gas when at least one conditions security of a padding parameter is not met.